LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA. 


.L  s. c 


Gl  FT    OF 


a. 


SL 


Lectures 


ON 


Building  Construction 


BY 


Captain  John  Stephen  Sewell 

Corps  of  Engineers,  United  States  Army 


DELIVERED  AT  THE 

United  States  Engineer  School  of  Application 
April  Q,  10,  and  //,  1903 


WASHINGTON   BARRACKS,  D.  C. 

PRESS    OF    THE    ENGINEER    SCHOOL 
1906 


Lectures 


ON 


Building  Construction 


BY 


Captain  John  Stephen  Jewell 

Corps  of  Engineers,  United  States  Army 


DELIVERED  AT  THE 

United  States  Engineer  School  of  Application 
April  9,  10,  and  II,  1903 


WASHINGTON  BARRACKS,  D.  C. 

PRESS    OF   THE    ENGINEER    SCHOOL 
1906 


G. 


LECTURES  ON  BUILDING  CONSTRUCTION 

*By  CAPTAIN  JOHN  STEPHEN  SEWELL 
Corps  of  Engineers,  U.  S,  Army 

DELIVERED  AT  THE  UNITED  STATES 
ENGINEER  SCHOOL  OF  APPLICATION 

APRIL  9,  10,  AND  11,  1903 

The  fundamental  principles  underlying  the  art  of  building  are  the  same 
as  those  governing  all  forms  of  construction.  To  one  well  versed  in  the 
principles  of  engineering  they  can  present  nothing  new,  except  in  their 
particular  mode  of  application.  So  much  has  been  written  and  printed  on 
the  art  of  building  that  it  might  seem  superfluous,  at  this  time,  to  add 
another  word.  Yet,  up  to  the  present,  the  design  and  erection  of  buildings 
has  been  a  matter  of  tradition,  precedent,  and  rule  of  thumb;  but  modern 
requirements  are  such  that  it  has  been  necessary  to  call  in  the  engineer  to 
the  assistance  of  the  architect;  as  this  is  a  thing  of  recent  development,  it 
is  possible  that  the  application  of  engineering  criteria  may  not  only  indicate 
the  way  to  safe  and  successful  development  of  features  not  founded  on 
precedent,  but  even  disclose  room  for  improvements  in  the  most  time- 
honored  rules  of  practice.  Architecture  is  a  matter  of  tradition  and  prece- 
dent; engineering  is  one  of  principles,  to  be  well  ascertained  and  established, 
and  then  logically  but  fearlessly  applied,  whether  along  old  lines  or  not. 

The  art  of  building  has  never  been  fully  discussed  from  the  engineer's 
standpoint,  and  it  is  not  proposed  herein  to  attempt  such  discussion,  but 
there  are  a  number  of  points  resulting  from  practical  experience  which 
will  be  touched  upon  with  a  view  to  supplementing  the  course  in  Building 
Construction  at  the  Engineer  School. 

Every  military  engineer  should  be  master  of  construction  in  all  its  forms. 
Probably  the  first  really  difficult  structures  erected  by  man  had  their  origin 
in  military  requirements;  so,  military  engineering  may  fairly  claim  to  be 
the  father  of  all  construction. 

Coming  to  buildings  proper,  there  was  not  a  great  amount  of  structural 
design  in  the  architecture  of  India,  Babylonia,  Egypt,  or  Greece.  With 
the  free  use  and  great  development  of  the  arch  and  dome  by  the  Romans, 
the  structural  aspect  of  buildings  became  more  interesting;  and  with  the 
development  of  the  Gothic  and  related  styles  of  architecture  there  appeared 
structural  skill  of  a  high,  order;  to  produce  the  wonderful  effects  seen  in 


1G9934 


the  old  cathedrals,  the  material  was  often  called  upon  to  do  its  utmost 
limit  of  work  and  there  was  an  accurate  adjustment  of  opposing  forces 
which  must  always  command  our  admiration.  Yet  the  design  was  such 
that  the  forces  had  always  to  be  counterbalanced  in  a  very  indirect  and 
costly  way.  Only  the  religious  enthusiasm  of  the  Middle  Ages  and  a 
fine  artistic  sense,  combined  with  the  modern  engineer's  skill,  without  his 
sense  of  economy,  could  have  produced  such  a  type  of  building.  The 
modern  architect  seems  often  to  have  inherited  the  artistic  sense  of  his 
medieval  predecessor — but  not  always  his  skill  as  a  structural  designer. 

With  buildings  of  the  simpler  and  cheaper  type,  the  engineer  has  not 
often  much  to  do;  yet.  they  present  many  interesting  points  in  construc- 
tion, though  not  requiring  any  great  amount  of  mathematics  in  their 
design. 

On  the  subject  of  frame  buildings,  little  can  be  added  to  Part  II  of 
Kidder's  Building  Construction  and  Superintendence.  Some  points 
brought  out  by  him,  however,  may  well  be  emphasized.  In  the  matter 
of  the  frame,  the  method  shown  in  Figure  19,  page  50,  could  hardly  be 
improved;  considering  cost  and  efficiency  together,  it  is  probably  the  best 
that  can  be  done.  The  importance  of  having  at  all  points  the  same 
amount  of  timber  capable  of  shrinking  in  a  vertical  direction  can  not  be 
overestimated.  The  lengthwise  shrinkage  of  timber,  while  by  no  means 
inappreciable,  is  not  enough  to  cause  cracks  in  plaster  or  to  spoil  the  fit  of 
doors  and  windows.  But  its  crosswise  shrinkage  is  a  very  different  mat- 
ter. If  one  end  of  a  partition  is  supported  on  6  inches  more  of  shrink- 
able  timber  than  the  other,  cracks  will  surely  appear  in  time,  and  the  fit  of 
doors  will  be  noticeably  impaired.  Where  inequalities  in  the  amount  of 
shrinkable  timber  are  inevitable,  it  would  be  well,  in  the  case  of  those 
members  whose  shrinkage  will  cause  trouble,  to  buy  kiln-dried  lumber, 
if  obtainable  in  suitable  sizes,  and  give  it  a  priming  coat  of  paint  before 
exposing  it  to  the  weather  in  the  unfinished  building.  Even  this  will  not 
entirely  cure  the  trouble,  but  it  will  greatly  lessen  it.  Thoroughly  aired 
seasoned  lumber  would  be  better,  but  it  can  not  always  be  obtained. 
Kiln  drying  is  of  doubtful  utility  in  large  pieces;  if  thoroughly  done,  it  is 
likely  to  cause  serious  checking;  if  not  thoroughly  done,  the  shrinkage  is 
not  taken  out,  and  ordinary  lumber  might  as  well  be  used.  The  expense 
of  kiln  drying  large  pieces  would  also  be  prohibitive  in  most  cases.  A 
certain  amount  of  shrinkage  and  a  few  cracks  in  a  frame  building  are 
probably  inevitable. 

The  method  shown  by  Kidder  for  the  support  of  an  interior  partition, 
in  Figure  62,  page  80,  is  one  of  the  few  mistakes  in  his  Part  II.  Parti- 
tions weigh  a  good  deal  themselves,  and  often  support  floors  above.  To 


depend  on  the  holding  power  of  a  lag  screw  under  a  direct  pull  is  not 
safe;  besides,  it  seriously  weakens  the  joists  at  the  most  vital  point. 

In  many  cases,  where  shrinkage  and  settlement  are  feared,  an  interior 
partition  might  be  built  as  a  truss,  so  as  to  carry  itself,  from  end  to  end, 
and  thus  be  independent  of  the  floor  joists  beneath  it;  but  probably  the 
end  supports,  in  a  frame  building,  would  be  as  liable  to  settlement  as  the 
joists.  A  reasonable  amount  of  care  and  money  expended  upon  fire  and 
vermin  stops  is  a  good  investment  The  underside  of  girts  and  partition 
caps  might  well  be  covered  with  tin,  where  they  are  exposed  between  the 
studs.  This  will  prevent  fire  from  attacking  these  members  until  the 
temperature  has  become  quite  high;  it  will  also  entirely  prevent  vermin 
from  weakening  them  by  gnawing.  A  rat  will  easily  gnaw  through  a 
piece  4  by  4  inches,  if  he  can  get  at  the  wood. 

In  addition  to  the  tin  underneath,  it  is  well  to  use  brick  nogging  above, 
so  as  to  prevent  the  horizontal  passage  of  fire  and  vermin  from  one  room 
to  another  between  the  floor  and  ceiling. 

The  roof,  even  of  a  frame  building,  is  much  better  covered  with  slate 
or  tin  than  shingles,  so  far  as  mere  utility  is  concerned.  Sparks  from 
chimneys  and  neighboring  conflagrations  are  much  less  liable  to  set  the 
house  on  fire,  and  slate,  at  any  rate,  will  last  much  longer  than  shingles. 
On  the  other  hand,  shingles  can  be  used  rt>  obtain  effects  that  are  very 
attractive,  and  in  isolated  houses  the  fire  risk  is  not  a  fatal  objection  to 
their  use.  Economy  often  compels  it. 

A  slate  or  tile  roof,  because  of  its  permanence,  is  worthy  of  copper  flash- 
ing; but  a  shingle  or  tin  roof  should  be  flashed  with  tin.  The  best  grades 
of  I  C  plates  should  be  used  for  this  purpose.  In  any  case,  the  flashing 
must  be  done  with  the  utmost  care;  rain  and  snow  are  thorough  inspectors; 
if  there  is  a  defect  in  the  flashing  they  will  surely  discover  it  and  announce 
the  fact  in  the  form  of  ruined  ceilings  and  falling  plaster.  Gutters  also 
must  be  well  designed  and  carefully  built.  In  latitudes  where  there  is 
much  real  winter,  the  best  forms  of  gutter  are  those  shown  in  Figures  129 
and  142,  Kidder's,  Part  II.  In  these  forms  the  freezing  of  the  gutter  can 
never  cause  water  to  back  up  under  the  roofing  and  appear  inside  of  the 
house. 

Chimneys  in  frame  houses  must  always  be  so  constructed  that  relative 
shrinkage  or  settlement  between  them  and  the  house  can  not  strain  either 
structure  or  impair  the  flashing.  No  part  of  the  brickwork  should  project 
over  or  have  a  bearing  on  any  part  of  the  timber  construction.  The 
chimney  should  be  a  separate  and  self-contained  structure,  including  the 
fireplaces,  but  not  the  hearths,  from  the  ground  up. 

When  buildings  have  brick  walls,  timber  floors,  and  timber  partitions, 


a  certain  inequality  of  shrinkage  is  generally  inevitable.  Partition  caps 
and  girders  are  bound  to  shrink;  so  are  floor  joists.  The  brick  walls  will 
shrink  if  they  are  laid  up  in  lime  mortar,  but  the  amount  of  shrinkage 
varies  in  different  cases  and  can  not  be  predetermined.  If  the  walls  are 
laid  in  cement  mortar,  as  they  should  be  in  all  Government  buildings  of 
any  importance  at  all,  the  shrinkage  of  the  masonry  will  be  negligible. 
Assuming  that  the  walls  will  not  shrink  appreciably,  the  problem  is  pre- 
sented of  preventing  shrinkage  elsewhere  from  throwing  floors  out  of 
level,  spoiling  the  fit  .of  doors  and  producing  unsightly  cracks.  One 
method  is  to  make  all  partitions  that  are  continuous  from  the  foundation  up 
of  brick ;  but  this  is  often  impossible  because  of  expense.  Even  if  this  is 
done,  there  will  be  other  partitions  that  must  be  supported  by  the  floors ; 
the  only  sure  remedy,  in  this  case,  is  to  use  a  steel  beam  to  carry  the  par- 
tition. In  the  case  of  the  partitions  that  are  continuous  from  the  founda- 
tions up,  serious  shrinkage  can  be  prevented  by  building  them  of  brick  to 
the  first  floor,  and  of  studding  above,  provided  the  studs  start  from  the 
bricks  in  the  first  story  and  are  supported  always  on  the  partition  caps 
above.  If  these  caps  are  of  timber  there  will  be  a  little  shrinkage,  but 
they  might  be  made  of  two  steel  angles  forming  a  sort  of  inverted  channel, 
and  secured  to  the  tops  of  the  studs,  in  each  case;  the  upper  studs  could 
be  secured  to  the  caps  by  lu$s  or  clips.  All  shrinkage  that  would  do  any 
harm  could  be  eliminated  by  supporting  all  partitions  and  the  ends  of  all 
floor  joists  on  a  system  of  steel  girders  and  beams  supported  in  turn  by  the 
brick  walls. 

If  any  of  the  methods  mentioned  above  are  applied  with  thoroughness, 
the  cost  of  the  building  will  be  materially  increased.  In  the  case  of  any 
building  small  enough  to  justify  the  use  of  studded  partitions  at  all,  the 
same  result  could  be  attained,  at  a  cost  slightly  greater  yet,  by  making  the 
floors  of  reinforced  concrete  and  omitting  wooden  joists  altogether.  This 
would  make  the  building  practically  fireproof,  and  in  all  cases  where  it  is 
likely  to  be  permanent,  even  if  it  is  only  a  set  of  quarters,  this  construc- 
tion should  be  adopted  if  sufficient  funds  are  available.  Where  the  walls 
are  of  brick,  the  conditions  are  favorable  for  trussed  partitions,  transferring 
their  load  to  their  ends.  If  firepoof  floors  and  steel  beams  are  both  out 
of  the  question,  much  can  be  accomplished  by  trussing  the  partitions,  even 
if  some  of  the  end  supports  are  timber  struts,  since  the  endwise  shrinkage 
is  of  small  importance.  If  well-seasoned  timber  girders  happen  to  be 
available  in  sufficient  numbers,  they  can  be  used  for  the  support  of  parti- 
tions and  floor  joists  and  will  greatly  lessen  shrinkage  cracks.  In  any 
case,  every  reasonable  precaution  should  be  taken  to  prevent  or  lessen 
these  cracks;  while  not  dangerous  to  the  structure,  they  are  unsightly  and 


are  a  refuge  for  vermin.  If  a  brick  house -is  not  furred  on  the  inside,  the 
angle  between  a  brick  wall  and  a  studded  partition  should  be  lathed  with 
wire  cloth  or  expanded  metal,  or  cracks  will  surely  appear. 

Fire  and  vermin  stops  are  just  as  important  in  a  brick  house  as  a  wooden 
one.  The  most  effective  form  is  a  fireproof  monolithic  floor,  stretching 
unbroken  from  wall  to  wall.  But  much  can  be  done  by  treating  studded 
partitions  in  the  manner  suggested  for  frame  houses;  and  if  the  walls  are 
furred  on  the  inside  the  brickwork  should  be  corbeled  out  as  far  as  the 
finished  plaster  surface,  from  a  point  one  course  below  the  joists  to  a 
point  one  course  above  them.  In  all  cases,  hot-air  flues  in  studded  par- 
titions should  be  made  of  bright  tin  or  galvanized  iron  and  kept  at  least 
1  inch  away  from  neighboring  studs  and  joists,  which  should  be  cov- 
ered with  tin  where  the  flue  passes  near  them.  The  lathing  over  the  flue 
should  be  of  wire  cloth  or  expanded  metal. 

The  roof  of  a  brick  building  should  always  be  of  tile  or  slate,  if  possible. 
If,  however,  the  roof  has  a  very  flat  slope,  and  in  any  case  if  money  is 
not  abundant,  some  form  of  sheet  metal  is  more  suitable  and  is  very 
generally  employed. 

The  metals  available  for  roofing  are  tin  plates,  copper,  zinc,  and  lead. 
Copper  and  tin  are  the  only  ones  that  are  commonly  employed  in  this 
country.  Zinc  is  said  to  be  used  a  good  deal  in  Belgium,  and  many 
European  nations  have  used  lead  quite  extensively.  It  is  doubtful 
whether  there  are  any  mechanics  in  the  United  States  thoroughly 
competent  to  work  in  either  zinc  or  lead. 

Copper,  besides  being  very  expensive,  has  a  very  high  coefficient  of 
expansion  and  contraction,  and  invariably  gives  trouble.  It  requires 
attention  all  the  time  on  this  account.  No  matter  how  much  allowance 
is  made  for  expansion  and  contraction,  it  appears  sooner  or  later  where 
not  expected,  and  is  a  continual  source  o'f  leaks.  However,  if  the  neces- 
sity for  frequent  inspection  and  small  repairs  is  accepted,  a  copper  roof  is 
very  durable  and  permanent,  and  is  not  by  any  means  to  be  condemned, 
if  there  is  money  to  pay  for  it.  Copper  is  probably  the  ideal  material  for 
flashing.  As  it  is  used  for  this  purpose  in  small  pieces,  usually  not 
soldered  together,  temperature  changes  are  not  a  source  of  trouble.  Cop- 
per for  roofing  and  flashing  should  be  hot  rolled,  so  as  to  be  soft,  and 
should  weigh  not  less  than  16  ounces  per  square  foot.  For  important 
work,  where  expansion  stresses  can  be  well  provided  for,  it  would  better 
weigh  20  ounces  per  square  foot.  Where  copper  is  used  for  gutters  and 
spouts  it  should  be  cold  rolled  and  weigh  not  less  than  16  ounces  per 
square  foot;  20  ounces  is  again  preferable,  if  expansion  troubles  can  be 
obviated.  Copper  is  sometimes  pressed  into  shapes  resembling  roofing 


6 

tiles,  and  when  used  in  this  way  is  very  durable  and  gives  no  trouble  from 
temperature  changes.  It  should  be  cold  pressed  so  as  to  be  as  stiff  as 
possible. 

Tin  roofing  plates  consist  of  sheets  of  black  iron,  dipped  in  a  molten 
mixture  of  lead  and  tin.  The  best  plates  are  made  by  a  process  known 
as  the  hand-dipped  palm  oil  process,  or,  sometimes,  as  the  "old  method." 
The  plates  are  pickled,  thoroughly  cleansed  and  annealed,  dipped  in  an 
oil  expressed  from  the  seeds  of  a  certain  variety  of  African  palm,  and  then 
dipped  in  the  mixture  of  lead  and  tin.  The  best  grades  are  not  submitted 
to  any  further  process,  except  sorting  and  packing.  Inferior  grades,  after 
dipping,  are  run  through  rolls,  which  reduce  the  coating  to  a  minimum 
thickness.  Great  skill  is  required  in  dipping  to  secure  uniform  distribu- 
tion of  the  coating;  when  this  is  accomplished,  and  the  plates  are  not 
subsequently  rolled,  the  thickness  of  the  coating  and  therefore  the  dura- 
bility of  the  plate  are  a  maximum.  In  some  plates  of  an  inferior  grade, 
acid  is  used  instead  of  palm  oil,  to  secure  adhesion  between  the  plates  and 
the  coating.  The  use  of  acid,  and  the  rolling  of  the  plates  after  dipping, 
are  devices  for  lessening  their  cost,  and,  in  this  case  at  least,  their  efficiency. 
The  only  really  cheap  tin  plate  is  the  best,  when  ultimate  economy  is  in 
view. 

Tin  plates  come  in  two  weights,  known  as  I  C  and  1  X.  The  differ- 
ence in  weight  is  in  the  iron,  and  not  in  the  coating.  I  C  is  the  lighter 
weight  and  is  usually  used  for  roofing;  I  X  is  heavier  and  is  used  for 
flashing,  for  gutters,  and  for  spouts.  Tin  plates  also  come  in  two  sizes, 
14  by  20  inches  and  20  by  28  inches.  For  roofing,  the  smaller  size  is 
more  expensive  to  lay,  but  is  also  preferable,  because  it  provides  more 
thoroughly  for  expansion.  All  good  tin  plates  are  stamped  with  the 
name  of  the  brand  and  the  maker.  A  box  contains  112  sheets;  it  should 
weigh  120  pounds  if  of  14  by  20  inch,  and  240  pounds  if  of  20  by  28  inch 
plates.  The  total  weight  of  coating  in  a  box  of  the  best  14  by  20  inch 
plates  is  about  20  pounds,  of  which  6  pounds  are  tin  and  14  pounds  are 
lead.  It  would  probably  be  possible  to  get  as  much  as  30  pounds  of  coat- 
ing on  a  box  of  14  by  20  inch  plates,  but  the  process  would  be  very  slow 
and  more  expensive  than  it  is  worth.  Plates  coated  with  tin  and  lead  are 
known  as  terne  plates ;  if  coated  with  tin  alone  they  are  called  bright 
plates;  the  leading  manufacturers  claim  that  bright  plates  are  not  as  durable 
in  a  damp  climate  as  terne  plates,  and  probably  the  claim  is  well  founded. 
After  the  plates  are  coated  they  have  to  be  carefully  sorted,  as  there  are 
always  some  defective  ones.  These  may  carry  the  full  weight  of  coating, 
but  have  it  unevenly  distributed,  in  which  case  they  are  not  as  good  as  if 
they  had  less  coating  uniformly  distributed.  The  defective  plates  result- 


ing  from  the  manufacture  of  any  brand  of  high-grade  terne  plates  are 
known  as  the  -'wasters"  of  that  brand. 

In  the  matter  of  using  the  plates,  a  standing  seam  roof  is  preferable,  if 
the  pitch  is  steep  enough.  Painting  on  the  underside  before  laying,  and 
on  the  outer  surface  after  laying,  should  not  be  neglected.  The  state- 
ment often  made  that  the  roof  should  be  allowed  to  show  slight  signs  of 
rust  before  painting  on  the  outer  surface  had  its  origin  in  ignorance,  if  in 
nothing  worse.  One  good  coat  on  the  underside  is  usually  considered 
sufficient;  but  two  would  be  better.  No  waterproof  paper  or  felt  should 
ever  be  used  under  a  tin  roof,  as  this  would  promote  condensation  and 
rusting  out  of  the  metal  from  the  underside.  Acid  should  never  be  used 
as  a  soldering  flux,  whether  for  tin  or  copper.  Copper  should  always  be 
tinned  where  it  has  to  be  soldered;  this  is  necessary  to  produce  the  requi- 
site adhesion  between  the  copper  and  the  solder.  The  tinning  need  be 
done,  of  course,  only  over  the  small  surfaces  to  which  the  solder  must  be 
actually  applied,  and  is  often  done  at  the  site  of  the  work  by  the  mechanics 
themselves.  All  soldered  joints  in  copper  work  must  be  made  very  heavy 
with  solder;  even  then  they  will  almost  inevitably  open,  sooner  or  later. 

Waterproof  felt  is  much  used  both  by  itself  and  in  connection  with 
other  materials  for  the  weather  finish  of  roofs.  Used  by  itself,  laid 
a  slight  lap  and  fastened  with  nails  and  tin  washers,  it  is  very  suitable 
for  temporary  buildings,  sheds,  workshops,  etc.,  and  is  very  cheap.  It 
may  be  swabbed  where  it  laps  with  a  waterproof  cement,  which  will 
add  to  its  efficiency  and  prevent  rain  from  driving  up  under  the  lower 
edges.  Laid  in  several  thicknesses,  with  heavy  swabbing  coats  between 
the  layers,  it  forms  a  very  durable  and  satisfactory  roof  finish.  It 
can  be  further  covered  with  gravel  or  tile,  laid  in  waterproof  cement 
or  mastic,  and  in  the  case  of  the  tiles,  with  all  vertical  joints  grouted 
with  Portland  cement.  A  roof  finish  like  this,  where  appearance  is 
not  important,  is  good  enough  for  any  building.  It  is  practicable  only 
on  comparatively  flat  roofs,  though  the  tile  can  be  used  on  slopes  as 
steep  as  iV.  The  best  and  most  durable  felt  is  made  entirely  of 
wool,  and  saturated  with  some  refined  asphalt  which  will  not  rot  in 
contact  with  water,  nor  dry  out  in  the  sun.  "Trinidad  asphalt  is  not 
suitable  for  this  purpose.  Of  asphalts  available  in  this  country, 
Alcatraz  and  Bermudez  are  the  best.  They  should  be  softened  with 
enough  residual  oil  from  the  distillation  of  petroleum  to  give  them 
the  necessary  fluidity,  but  no  more.  An  asphaltic  cement  for  use 
with  this  felt  is  made  of  the  same  material  as  the  saturating  com- 
pound; if  it  is  to  be  applied  hot,  it  is  made  quite  stiff.  But  by  mix- 
ing the  compound  with  naphtha  or  benzine,  it  can  be  made  fluid 


enough  to  apply  cold;  the  evaporation  of  the  solvent  leaves  a  thin 
uniform  coat  of  the  compound,  which  will  preserve  its. flexibility  and 
waterproof  qualities  for  a  long  time,  if  not  subjected  to  mechanical 
injury. 

Tarred  felt,  and  swabbing  coats  of  coal  tar,  are  more  commonly 
used  than  asphalt  felts  and  cements.  But  coal  tar  is  so  devitalized  by 
the  extraction  of  the  components  useful  for  the  manufacture  of  aniline 
dyes,  perfumes,  flavoring  extracts,  etc.,  that  the  part  of  it  that  finds 
its  way  into  the  market  in  tar  papers  and  felts  lasts  but  a  short  time; 
moreover,  tar  felts  and  papers  nearly  always  contain  much  vegetable 
fiber,  which  is  not  nearly  so  durable  as  wool.  Asphalt  felts  and 
cements  cost  only  a  little  more,  and  should  always  be  used. 

There  is  a  felt  in  the  market,  known  as  Paroid,  manufactured  by 
F.  W.  Bird  &  Son,  of  East  Walpole,  Mass.,  which  the  makers  claim 
is  a  pure  wool  felt,  saturated  with  Alcatrez  asphalt.  If  this  is  true,  it 
is  as  good  a  felt  as  can  be  made.  There  are  several  brands  that  are 
saturated  with  Trinidad  asphalt,  but  they  are  hardly  better  than  good 
tarred  felts.  The  makers  of  the  Paroid  roofing  felt,  not  only  saturate 
the  felt  with  their  asphaltic  compound,  but  also  coat  it  on  both  sides 
with  their  liquid  cement,  which  they  sell  under  the  name  of  Parine 
cement  liquid.  They  further  roll  a  dusting  of  powdered  soapstone 
into  both  surfaces,  to  prevent  the  felt  from  being  sticky. 

In  addition  to  copper  and  tin,  corrugated  iron,  both  black  and  gal- 
vanized, is  often  used  for  roofs;  but  it  is  not  cheap — it  is  ugly,  and 
possesses  no  advantages  except  for  permanent  shops  where  it  is  desired 
to  fasten  the  weathering  of  the  roof  directly  to  the  steel  framework, 
without  fire  protection  of  any  kind. 

In  the  use  of  all  sheet  metal  roofs,  great  care  must  he  taken  to  pre- 
vent the  wind  from  taking  off  the  metal  covering.  Corrugated  iron 
must  be  very  firmly  fastened  down,  for  it  is  not  practicable  to  keep 
the  wind  from  under  it.  Copper  and  tin  roofs  must  be  turned  down 
at  the  eaves  and  closely  tacked  along  the  edges,  or,  in  some  cases, 
soldered  to  the  gutter,  to  prevent  the  wind  from  getting  under  it. 
Otherwise,  a  violent  storm  will  roll  it  up,  pulling  the  nails  as  it  goes, 
and  end  by  stripping  the  entire  roof  covering  off,  in  an  astonishingly 
short  time. 

Of  the  various  forms  of  roof  covering  described,  copper  and  the 
tiles  laid  on  an  asphalt  base  are  really  too  expensive  for  non-fireproof 
buildings;  of  the  others,  a  simple  felt,  of  single  thickness,  without 
a  swabbing  coat,  is  the  cheapest.  In  a  general  way,  shingles  come 
next,  then  tin,  and  then  slate  or  roofing  tiles.  The  latter,  when  used 


UNIVERSITY   fl 
7 


9 

in  highly  ornamental  forms,  may  be  very  expensive,  but  are  often  used 
in  non-fireproof  buildings  of  a  high  class  for  architectural  effects. 

So  far,  only  those  points  have  been  touched  upon  which  pertain 
peculiarly  to  such  buildings  as  ordinary  dwellings,  whether  of  wood 
or  brick.  Many  other  matters,  such  as  paint,  plumbing,  heating, 
hardware,  dampproofing,  quality  of  finish,  lighting,  etc.,  are  of 
importance,  but  must  be  discussed  in  connection  with  fireproof  work, 
and  can  then  be  best  discussed  for  all  classes  of  buildings.  Before 
leaving  the  subject  of  non-fireproof  buildings,  however,  a  few  points 
should  be  brought  out  relative  to  mill  construction,  or,  as  it  is  some- 
times called,  slow-burning  construction.  This  is  quite  sufficiently 
well  described  in  current  literature,  and  complete  general  specifica- 
tions for  its  design  can  always  be  obtained  by  simply  addressing  a 
request  to  Mr.  Edward  Atkinson,  of  Boston,  Mass.,  who  was  largely 
instrumental  in  introducing  it,  and  has  a  missionary's  zeal  in  dis- 
seminating information  in  regard  to  it.  This  construction  has  for 
its  most  essential  points  the  use  of  none  but  large  timbers  and  the 
avoidance  of  all  cellular  or  hollow  construction,  such  as  studded  par- 
titions, covered  with  either  plaster  or  matched  boarding.  It  neces- 
sarily involves  the  use  of  iron  or  steel  post  caps,  joist  hangers,  etc. 
A  great  variety  of  these  devices  can  be  had  in  stock,  guaranteed  by 
their  makers  to  be  safe  under  specified  loads.  The  main  point  is 
that  these  guarantees  are  usually  worthless.  Every  engineer  who 
adopts  mill  construction  must  use  them,  but  he  should  carefully  calcu- 
late their  strength  against  shearing  and  bending  at  every  point,  for 
many  current  designs  are  produced  by  mere  rule  of  thumb  and  are 
fatally  weak  at  some  point.  Another  thing  about  mill  construction 
is  that  it  is  not  slow  burning  at  all;  it  might  be  very  properly  called 
slow  igniting,  for  that  would  be  a  truthful  description.  Large 
timbers  are  slow  to  ignite,  and  with  every  nook  and  corner  open  to 
view,  there  is  much  less  probability  of  a  fire  starting  and  getting  be- 
yond control  before  discovery;  combined  with  a  thorough  automatic 
sprinkler  installation,  a  mill  construction  building  is  comparatively 
safe  from  destruction  by  fire.  But  once  a  fire  gets  a  fair  start  in  it, 
it  is  doomed  to  certain  and  speedy  destruction.  There  are  long  lists 
of  such  catastrophes,  such  as  the  destruction  of  the  Capital  Traction 
Company's  power  house  at  Fourteenth  and  E  streets,  in  this  city, 
some  years  ago.  It  usually  takes  from  thirty  minutes  to  an  hour  for 
the  complete  destruction  of  a  four  to  six  story  building  occupying 
an  entire  block.  One  reason  probably  is  that  no  available  timber  but 
long  leaf  pine  can  be  secured  in  sufficiently  large  sizes  at  a  reasonable 


10 

price.  Once  fairly  started,  it  burns  with  almost  explosive  violence, 
and  nothing  can  save  it.  The  people  who  live  in  the  long  leaf  pine 
belt  never  use  this  timber  in  their  stoves,  if  they  can  help  it,  because 
it  burns  so  furiously  it  soon  destroys  the  stoves,  besides  making  a 
proper  control  of  the  temperature,  whether  for  cooking  or  heating, 
quite  out  of  the  question. 

One  point  that  should  never  be  neglected  in  any  brick  building, 
with  timber  floors,  is  the  cutting  of  the  wall  ends  of  girders  and 
joists  on  a  bevel,  to  prevent  throwing  the  wall  by  the  breaking  of  the 
joist  or  girder  when  burned  through  in  a  fire.  Anchors  in  such  cases 
should  be  fastened  near  the  bottom  of  the  beam,  preferably  with  one 
large  bolt,  just  inside  the  wall  line.  Then,  when  the  beam  falls, 
even  if  it  hangs  by  the  anchor,  it  can  freely  revolve  downwards  with- 
out bringing  any  leverage  on  the  walls.  Where  the  load  of  a  joist 
or  girder  does  not  require  bearing  plates  or  templates  to  distribute 
the  pressure,  the  course  immediately  under  the  beam  should  be  a  header 
course,  otherwise  severe  shocks  and  vibrations  might  cause  the  bricks 
to  loosen  and  slip  out  of  the  wall.  Major  Abbot  observed,  after  the 
Charleston  earthquake,  that  this  was  a  very  vital  point.  Where  the 
ends  of  the  joists  rested  on  header  courses,  they  invariably  remained 
in  place,  tut  very  often,  where  the  joists  rested  on  a  stretcher  course, 
the  bricks  slipped  out  and  allowed  the  floors  to  drop. 

There  are  some  advantages  in  corbeling  out  a  shelf  to  receive  the 
ends  of  joists,  provided  the  corbeling  is  not  objectionable  on  artistic 
grounds,  and  is  well  done.  It  should  project  about  1  inch  to  a 
course,  be  made  entirely  of  headers,  and  be  only  wide  enough  to  give 
the  requisite  bearing.  On  the  whole,  however,  in  a  well-built  wall, 
it  is  better  to  let  the  girders  and  joists  project  into  the  wall,  leaving 
a  small  space  on  the  sides  and  top  for  ventilation.  This  insures 
greater  unity  of  the  structure,  and  applies  the  load  nearer  to  the 
center  of  the  wall.  If  heavy  loads  call  for  templates  or  bearing 
plates,  it  is  better  to  put  them  entirely  within  the  wall,  at  least  2 
inches  back  from  the  face,  to  avoid  concentrated  pressure  at  the  inner 
edge.  It  is  also  well,  in  such  cases,  to  support  the- end  of  the  beam 
on  a  small  plate  in  the  center  of  the  bearing  plate  or  template,  to 
prevent  deflection  in  the  beam  from  disturbing  the  distribution  of 
pressure.  It  is  to  be  observed  that  the  usual  method  of  reducing  the 
thickness  of  the  wall  as  the  upper  stories  are  reached,  by  dropping 
off  half  a  brick  at  a  time  on  the  inside,  has  a  beneficial  effect  in 
counteracting  the  eccentricity  of  the  floor  loads;  corbeling  always 
increases  this  eccentricity,  and  that  alone  should  condemn  it,  where 


11 

very  heavy  loads  must  be  carried.  It  seems  entirely  possible,  and  even 
probable,  that  advances  in  fireproof  construction  will,  before  long, 
displace  mill  construction  in  all  important  factory  buildings.  While 
this  is  a  consummation  much  to  be  desired,  mill  construction  has 
played  an  important  role,  and  will  always  be  looked  upon  as  a  long 
step  in  advance,  taken  at  a  time  when  there  was  urgent  need  of  it. 

FIREPROOF  BUILDINGS 

It  is  in  buildings  so  large  and  important  that  carrying  the  weights  is  a 
serious  matter,  and  fireproof  construction  is  considered  necessary, 
that  the  civil  engineer  first  becomes  indispensable.  Many  of  the 
improvements  in  design,  and  execution  introduced  by  him  in  such 
structures,  are  applicable  also  to  the  smaller,  non-fireproof  buildings 
and  if  applied  would  produce  much  better  results  than  those  com- 
monly attained,  without  increase  of  cost.  Where  such  points  are 
brought  out,  their  application  to  less  important  buildings  will  be  indi- 
cated. 

The  first  question  in  any  building  is  the  plan.  This  is  mani- 
festly determined  by  the  uses  to  which  the  building  is  to  be  put,  and  the 
space  within  which  it  must  be  confined.  It  must  be  so  arranged  as 
to  be  fit  for  its  purpose,  yet  not  inconsistent  with  a  suitably  artistic 
treatment  of  the  elevations.  Right  here  is  where  the  architect,  en- 
gineer, and  owner  often  clash.  Architects  lay  great  stress  upon  the 
plan,  and  are  very  jealous  of  their  jurisdiction  over  it.  This  is  quite 
natural,  for  a  poor  plan  may  make  good  architectural  treatment  im- 
possible; yet,  the  architect  is  apt  to  lay  undue  stress  upon  the  artistic, 
and  to  overlook,  neglect,  or  deliberately  sacrifice  convenience  and 
utility.  The  engineer  and  owner  are  apt  to  consider  the  latter  points 
first,  and  not  to  give  due  consideration  to  the  former. 

As  an  example  of  what  the  architect  will  do,  if  unrestrained,  one 
of  the  most  prominent  architects  of  Washington,  in  making  plans 
for  a  hospital  building  recently,  located  the  dumb  waiter  40  feet 
from  the  kitchen,  and  stopped  it  off  at  the  third  floor,  although  there 
was  a  ward  on  the  fourth  floor,  designed  for  thirty  or  forty  patients. 
How  they  were  to  be  fed,  and  the  directness  of  the  service  to  all  the 
floors,  were  not  considered  at  all.  The  fact  remains,  however,  that 
in  the  majority  of  cases,  the  architect  should  make  the  plan;  but  he 
should  be  compelled  to  change  it,  if  necessary,  until  it  not  only  satis- 
fies the  artistic  requirements,  but  the  utilitarian  ones  as  well.  There 
is  always  some  solution  reasonably  good,  from  all  points  of  view,  and 


12 

if  the  engineer  has  any  control  at  all,  he  should  see  to  it  that  this 
solution  is  finally  worked  out.  Making  floor  plans  for  buildings  is 
not  a  simple  matter — not  even  for  a  small  dwelling.  It  should  re- 
ceive the  most  careful  consideration  from  all  concerned,  if  the  highest 
efficiency  is  to  be  attained. 

The  floor  plans  having  been  fixed,  the  architect  will  soon  have  the 
elevations,  in  skeleton  form,  at  least,  for  these  must  be  considered, 
along  with  the  plans,  before  the  latter  can  really  be  fixed.  With  the 
plans  and  preliminary  elevations,  the  engineer  is  ready  to  begin,  in 
some  detail,  his  own  peculiar  work.  The  floors  and  interior  parti- 
tions always,  and  the  exterior  walls  generally,  in  a  modern  building, 
will  be  carried  by  the  framework,  which  is  usually  of  steel.  The 
first  task  is  to  locate  the  columns.  This  has  to  be  done  with  a  view 
to  the  interior  subdivision  and  finish,  as  a  matter  of  course.  Next 
must  be  considered  the  system  of  girders  and  beams  by  which  the 
floor  loads  are  carried  and  finally  concentrated  at  the  columns.  Then 
the  loads  imposed  on  the  columns  at  each  floor  must  be  calculated. 
They  should  be  divided  into  live  and  dead.  The  former  comprises 
the  entire  superimposed  floor  load,  and  the  latter  the  weight  of  con- 
struction. The  dead  load  can  not  always  be  calculated  accurately  until 
two  or  three  preliminary  designs  have  been  made,  since  the  design 
itself  determines  part  of  the  dead  load.  It  is  possible  to  assume 
quite  closely  what  the  dead  load  will  be,  however,  for  a  given  class  of 
building,  and  usually  one  preliminary  design  and  one  corrected  one, 
will  be  sufficient.  Having  the  column  loads,  the  foundations  can 
be  designed.  If  the  external  walls  are  not  carried  on  the  framework, 
they  will  still  start  from  the  same  foundations  as  the  wall  columns 
and  thus  their  weight  must  be  carried  at  the  bottom  just  the  same  as 
if  it  were  part  of  the  column  load  proper.  Where  a  building  is  of 
moderate  height  and  has  heavy  walls,  no  steel  columns  need  be  used; 
the  ends  of  girders  and  beams  would  be  borne  by  the  walls,  and  thus 
the  floor  loads  would  go  from  the  outer  bearings  of  girders  and  beams 
to  the  exterior  foundations  through  the  walls  themselves.  But  the 
foundation  problem  would  not  be  essentially  different  from  that  pre- 
sented by  a  building  with  steel  wall  columns,  carrying  either  the 
floors  alone  or  both  the  floors  and  the  walls. 

In  designing  the  foundations,  the  first  requisite  is  a  knowledge  of 
the  nature  of  the  strata  upon  which  they  are  to  rest.  Certain  and 
definite  knowledge  upon  this  point  is  difficult  and  often  expensive  to 
obtain.  If  some  engineer  or  physicist  could  devise  a  reasonably  simple 
system  whereby  from  physical  analysis  of  a  soil  its  power  to  carry 


13 

loads  could  be  predicted  within  100  per  cent.,  he  would  earn  the 
gratitude  of  all  future  generations  of  engineers.  It  is  not  in  the  least 
likely  that  this  will  ever  be  accomplished. 

There  are  various  ways  of  securing  information  as  to  the  strata 
underlying  a  proposed  structure.  Borings  are  the  -most  obvious,  as 
well  as  the  quickest  and  cheapest  of  all  methods  yielding  results  of 
any  value.  But  even  borings  are  very  deceptive;  they  often  miss 
the  vital  and  controlling  feature  of  the  whole  situation,  even  when 
very  close  together.  Actual  "excavations  or  test  pits  carried  to  sub- 
grade,  or  deeper,  are  better  than  borings,  and  more  expensive.  Only  the 
excavation  of  the  foundation  trenches  or  pits  themselves  will  disclose 
the  whole  truth,  and  even  they  often  fail  to  reveal  it  all.  When  the 
structure  is  of  any  importance,  the  excavation  should  be  carried  to 
sub-grade,  over  the  entire  area  probably  required  for  foundations,  then 
borings  and  occasional  pits  should  be  carried  still  deeper,  and  full- 
sized  tests  of  the  bearing  power  should  be  made,  if  possible. 

The  object  of  the  foundation  is  to  so  distribute  the  weight  of  the 
building  and  its  contents  to  strata  in  position  that  there  will  either 
be  no  settlement  at  all,  or,  if  there  must  be  settlement,  that  it  shall 
be  uniform.  If  there  is  any  hope  of  limiting  the  settlement  to  zero 
or  to  a  negligible  quantity,  it  should  be  done,  even  at  a  considerable 
expense.  A  poor  superstructure  will  stand  a  long  time  on  a  good 
foundation;  but  no  sort  of  superstructure  can  stand  intact  on  a  poor 
foundation.  Therefore,  it  is  better  to  make  the  foundation  good, 
even  if  it  has  to  be  done  by  skinning  down  what  goes  on  top  of  it. 

Of  the  various  materials  likely  to  be  met  in  constructing  foundations, 
solid  rock,  gravel,  hard  pan  (i.  e.,  a  consolidated  mixture  of  clay, 
sand,  and  gravel),  beds  of  bowlders,  and  reasonably  coarse  clean  sand 
need  never  give  any  anxiety,  provided  there  is  nothing  soft  beneath 
them.  They  will  all  carry  loads  of  from  three  to  fifty  tons  per  square 
foot  with  perfect  safety.  A  load  of  from  three  to  six  tons  per  square 
foot  will  always  result  in  footings  of  a  reasonable  size,  so  there  is  no 
need  of  extravagant  designs.  Of  the  materials  named,  sand  is  the 
only  one  that  calls  for  much  investigation;  yet  it  would  be  well  always 
to  build  an  experimental  pier  like  the  probable  footings,  and  load  it 
if  possible,  until  settlement  begins.  Such  tests  should  last  for  several 
days,  at  least,  as  the  yielding  of  some  soils  is  very  gradual,  but,  un- 
fortunately, none  the  less  certain. 

It  is  generally  assumed,  no  doubt  correctly,  that  when  pressure  is 
applied  to  a  certain  area  of  the  top  surface  of  a  given  stratum,  it 
spreads  laterally  as  it  is  transmitted  downwards,  so  that  the  successive 


14 

areas  which  feel  its  effects  become  constantly  larger.  The  angle  of 
spread  for  a  given  material  can  not  be  certainly  determined.  It  will 
be  seriously  modified  if  adjacent  areas  at  the  surface  are  also  loaded; 
let  it  be  denoted  by  0,  and  be  measured  from  vertical  planes  through 
the  edges  of  loaded  area  at  the  surface;  let  it  be  considered  positive 
when  it  is  really  an  angle  of  spread.  It  is  possible  that  0  may  be 
reduced  to  0  or  perhaps  even  to  a  negative  value,  by  reason  of  adjacent 
surface  loads.  In  the  latter  case,  it  is  almost  certain  that  the  bearing 
power  would  be  exceeded,  and  there  would  be  settlement  over  the 
entire  surface  of  all  structures,  both  old  and  new.  Sometimes  the 
strata  near  the  surface  are  able  to  bear  the  superimposed  loads,  and  even 
though  there  are  weaker  strata  below,  0  may  have  such  a  value  that 
the  pressure  is  distributed  over  a  sufficient  area  of  the  softer  lower 
strata,  to  enable  them  also  to  carry  it.  This  is  true  for  an  isolated 
structure.  If  other  adjoining  structures  are  erected  afterwards,  the 
area  of  the  softer  strata  available  for  carrying  the  first  structure  will 
be  diminished,  and  settlement  of  both  old  and  new  works  may  follow. 
In  the  case  of  a  mortar  battery  built  by  Major  Abbot  at  Charleston, 
the  overlying  stratum  was  sand,  and  it  was  about  10  feet  thick.  It 
bore  on  small  areas,  unit  pressures  at  least  as  great  as  those  due  to 
the  battery,  without  a  sign  of  settlement.  But  when  the  larger  area 
occupied  by  the  battery  was  loaded,  settlement  followed  to  the  extent 
of  2  feet  and  some  inches.  The  necessary  precautions  for  securing 
uniform  settlement  were  observed,  however,  and  the  structure  reached 
its  final  level  without  serious  cracks  or  damage.  To  illustrate  the 
principle  involved,  suppose  that  0  has  such  a  value  in  a  given  case 
that  the  pressure  has  spread  2  feet  all  around  when  it  reaches  the  soft 
lower  stratum.  Suppose  a  test  load  on  the  surface  is  applied  to  an 
area  1  foot  square.  It  will  spread  over  an  area  at  the  lower  stratum 
bounded  by  a  figure  consisting  approximately  of  a  square  5  feet  on  a 
side,  with  its  corners  cut  off  by  quadrants  tangent  to  the  sides,  having 
a  radius  of  2  feet,  and  centers  located  on  the  diagonals  of  the  square. 
This  area  will  be  about  21  square  feet.  Now  suppose  that  the  area 
at  the  surface  is  10  feet  square.  The  area  below,  even  if  the  corners 
are  not  rounded  off,  will  be  only  14  by  14,  or  196  square  feet — 
not  twice  as  much  as  the  surface  area,  whereas  in  the  other  case,  it 
was  twenty-one  times  as  much.  The  conditions  illustrated  here  may 
occur  on  city  blocks,  as  the  city  becomes  more  closely  built,  and  new 
structures  are  erected  in  juxtaposition  to  existing  ones.  If  the  softer 
lower  strata  are  compressible,  settlement  of  both  old  and  new  works 
may  follow.  On  the  other  hand,  if  the  soft  strata  are  saturated  with 


15 

water,  they  will  be  incompressible.  Settlement  will  then  be  impos- 
sible, unless  the  material  can  escape  laterally  or  both  laterally  and 
vertically.  If  the  whole  of  a  large  area  is  loaded,  bdth  of  these  things 
may  be  prevented,  and  the  load  will  be  carried  on  the  same  principle 
as  the  pressure  on  the  piston  of  a  hydraulic  jack.  The  condition  is 
one  of  unstable  equilibrium,  however,  and  is  not  by  any  means 
desirable.  Strata  that  are  soft  and  filled  with  water,  act  partly  like 
liquids  and  partly  like  solids.  If  they  are  loaded  vertically,  and  can 
not  yield  laterally,  they  may  bulge  up  around  the  loaded  area,  causing 
settlement  of  the  latter.  This  can  be  prevented  by  properly  loading 
the  areas  likely  to  bulge  up;  but  just  what  load  per  square  foot  will  be 
required  and  how  much  of  the  adjacent  area  must  be  loaded  would  be 
difficult  to  determine  in  any  case,  and  must  be  largely  a  matter  of 
judgment  and  experience. 

In  testing  soils,  it  should  be  remembered  that  when  only  a  small 
area  at  the  surface  is  tested,  the  pier  or  post  used  for  applying  the  load 
will  often  have  a  sort  of  punching  effect  and  begin  to  settle  under 
unit  loads  which  would  be  perfectly  safe  over  large  areas.  Sand,  with 
water  in  it,  will  slip  out  from  under  a  test  pier  or  post,  and  the  test 
load  will  work  downwards  when  it  does  not  amount  to  10  per  cent, 
of  what  the  sand  would  carry  under  an  actual  structure.  It  is  evident 
from  all  that  has  been  said  that  the  results  of  tests  on  the  bearing 
power  of  soils  must  be  used  with  judgment.  The  very  same  results 
might  follow  from  a  given  method  of  testing  in  soils  of  widely  vary- 
ing bearing  power. 

It  is  useless  to  add  in  this  paper  anything  on  the  ordinary  methods 
of  increasing  the  bearing  power  of  a  compressible  soil.  They  are  all 
thoroughly  described  in  current  literature.  It  might  be  useful  to  say, 
however,  that  when  tests  show  manifest  compression  of  the  surface 
strata,  under  loads  approximating  those  desired  to  be  used  in  practice, 
it  is  better  to  adopt  some  mode  of  treatment  at  once.  The  same  is 
true  of  unyielding  strata  overlying  soft  ones,  unless  the  thickness  of 
the  former  is  sufficient  to  guarantee  the  load  against  breaking  through. 

If  it  is  decided  to  use  wooden  piles,  they  must  be  cut  off  below 
the  water  line,  to  insure  permanence.  If  this  is  inconvenient  or 
expensive,  concrete  piles  may  be  used,  which  do  not  depend  upon  the 
condition  of  the  soil  for  their  durability.  Great  progress  is  being 
made  in  the  use  of  concrete  piles  or  piers  put  down  like  piles.  All 
the  student  officers  should  observe  and  make  notes  of  the  method  now 
in  use  at  the  site  of  the  officers'  quarters  for  the  Engineer  School, 
as  it  is  a  very  simple  and  economical  one — scarcely  more  expensive 


16 

than  wooden  piles.  The  conditions  here  are  as  follows:  A  fill  of 
from  10  to  14  feet  of  argillaceous  material,  settling  seriously  under 
loads  of  from  500  to  1,000  pounds  per  square  foot;  a  firm  stratum  of 
sand  below  the  fill,  of  unknown  depth,  but  certainly  good  for  the  loads 
likely  to  be  brought  upon  it  by  the  officers'  quarters.  If  wooden  piles 
were  used,  they  would  surely  decay,  for  the  fill  is  sometimes  wet  and 
sometimes  dry.  Nothing  would  be  gained  by  driving  them  and  cut- 
ting them  off  at  the  level  of  the  water  line,  for  this  would  carry  the 
excavation  to  the  firm  sand,  which  can  carry  the  load  without  piles.  If 
the  excavation  were  carried  to  the  sand,  it  would  be  quite  expensive, 
and  would  necessitate  a  very  large  mass  of  concrete  to  bring  the  foun- 
dations up  to  the  basement  floor  levels.  By  the  use  of  concrete  piles, 
the  weight  can  be  transferred  to  the  sand  at  much  less  expense,  and 
there  is  no  doubt  as  to  the  durability  of  the  piles.  In  this  case,  the 
piles  clearly  act  as  columns,  deriving  some  lateral  support  from  the 
surrounding  earth,  but  transmitting  their  loads  by  direct  compression, 
nevertheless.  It  often  happens,  however,  that  a  pile  driven  fairly  deep  in 
very  soft  material  will  carry  a  heavy  load,  without  reaching  a  firm  bear- 
ing at  all.  A  group  of  piles,  in  such  material,  will  often  carry  a  load 
that  would  sink  out  of  sight  if  distributed  directly  over  the  area 
occupied  by  the  piles.  Just  why  this  occurs  is  a  little  obscure;  it  is 
not  certain  that  it  could  always  be  duplicated.  In  a  case  of  this  sort 
on  the  river  front  of  New  York,  as  nearly  as  the  writer  can  remember, 
as  it  was  related  to  him  verbally,  an  average  of  one  pile  to  a  certain 
number  of  square  feet,  driven  in  the  mud,  but  not  to  a  firm  bearing, 
had  been  carrying  a  certain  load  per  pile  for  a  long  time.  It  was 
decided  to  increase  the  size  and  weight  of  the  superstructure,  and  to 
provide  for  it,  more  piles  were  driven  between  the  old  ones,  but  when 
the  new  and  heavier  load  was  applied,  the  entire  piled  area  settled 
quite  seriously. 

Apparently  the  piles  distribute  the  load  by  skin  friction  throughout 
a  certain  volume  of  the  materials.  It  will  stand,  when  reinforced  in 
this  way,  a  certain  amount  of  stress  without  deformation,  but  beyond 
this  it  is  not  possible  to  go.  Some  very  remarkable  statements  as  to 
the  bearing  power  of  piles  when  driven  in  what  seemed  almost  liquid 
mud  can  be  found  in  Patton's  Foundations.  There  is  some  law  here, 
quite  obscure  and  unknown  at  present,  which  would  be  very  valuable 
if  fully  disclosed.  Possibly  the  piles  tie  together  a  large  volume  of 
the  soft  material,  compelling  it  to  act  as  a  unit,  giving  it  strength 
against  deformation,  and  at  the  same  time  making  available  a  sort  of 
buoyancy  that  it  must  have  in  its  semi-liquid  surroundings.  At  any 


17 

rate,  piles  that  have  been  settled  into  place  under  the  mere  weight 
of  the  ram,  have,  after  a  few  days,  borne  loads  ten  or  twelve  times  as 
great  as  the  ram,  without  further  settlement.  This  seems  almost  in- 
credible, but  is  apparently  true,.  It  would  hardly  be  safe  practice  to 
count  on  it,  however,  without  tests  in  each  individual  case. 

As  a  rule,  the  most  suitable  material  for  foundations  is  concrete. 
This  material,  when  tested  to  destruction  under  compression,  gen- 
erally fails  by  shearing  along  planes  making  an  angle  of  about  30° 
with  the  direction  of  the  applied  force.  Holes  punched  through 
slabs  of  concrete  generally  increase  in  size  as  they  pass  through,  at 
about  the  same  rate.  It  is  well  to  spread  concrete  foundations  at  the 
same  rate,  as  by  this  means  all  tensile  stresses  will  be  avoided.  This 
leads  to  rather  heavy  foundations,  but  it  is  certainly  safe  practice,  and 
none  too  good  for  important  buildings.  It  should  be  remembered 
that,  regardless  of  unit  pressures,  every  wall  should  have  a  footing 
appreciably  wider  than  itself  to  insure  stability. 

In  commercial  office  buildings,  where  settlement  is  expected,  it  is 
customary  to  proportion  the  footings  under  different  parts  of  the 
buildings  according  to  the  dead  load  alone.  But  in  important  Govern- 
ment buildings  the  foundations  should  first  be  made  secure  against 
settlement,  if  possible,  and  then  proportioned  everywhere  for  the 
total  load.  The  live  load  will  not  be  as  likely  to  produce  settlement 
as  a  dead  load  of  the  same  amount.  If  settlement  is  inevitable,  a 
grillage  over  the  entire  site  stiff  enough  to  resist  distortion  under  the 
varying  concentrated  loads  of  columns  and  piers  is  the  best  solution, 
but  it  is  very  expensive.  The  next  best  plan  is  to  find  out  what  the 
average  actual  total  load  will  be,  and  proportion  for,this.  Where  the 
live  load  is  considerable  and  subject  to  much  variation,  it  would  be 
very  hard  to  hit  upon  any  method  that  would  insure  uniform  settle- 
ment, short  of  preventing  settlement  altogether. 

If  steel  beam  grillages  are  necessary  to  spread  the  pressure  under 
columns  and  walls  over  a  sufficient  area,  they  should  be  kept  above  the 
ground  water  level  if  possible,  and  very  carefully  and  thoroughly  bed- 
ded in  Portland  cement  concrete  to  avoid  corrosion.  The  best  plan  is 
to  avoid  the  use  of  beams  altogether,  if  possible. 

Within  recent  years  foundations  carried  to  the  solid  rock  by  means 
of  pneumatic  caissons  have  been  used  in  some  important  buildings. 
In  several  cases  in  New  York,  where  it  was  desired  to  have  several 
stories  of  cellars  below  the  water  line,  the  entire  site  has  been  sur- 
rounded with  rectangular  caissons,  separated  from  each  other  by  guid- 
ing angles,  forming  a  pocket  between  the  caissons.  The  caissons 


18 

were  filled  with  concrete,  and  the  pockets  were  rammed  full  of  clay 
puddle;  the  bottom  of  the  excavation  was  pumped  out,  floored  with 
concrete,  and  a  layer  of  waterproofing,  and  then  -enough  more  con- 
crete to  resist  the  upward  pressure  of  the  water.  In  this  way  immense 
volumes  of  storage  space  have  been  made  available  at  depths  of  20  or 
30  feet  below  the  water  line. 

One  troublesome  class  of  operations  often  encountered  in  founda- 
tion work  is  the  underpinning  of  existing  structures.  In  Kidder's 
Building  Construction,  Part  I,  and  in  other  works,  many  methods 
are  shown  for  temporarily  supporting  the  old  structures  while  the  new 
work  is  going  in  under  them;  but  the  most  interesting  and  difficult 
part  of  the  whole  operation  is  getting  the  temporary  supports  in  with- 
out allowing  the  old  work  to  settle  or  collapse.  On  this  point  very 
little  is  to  be  found  in  current  literature.  It  is  necessary  to  put  in  the 
temporary  supports  so  that  they  will  not  interfere  with  the  new  work 
nor  be  disturbed  by  it.  This  often  involves  an  excavation  close  up 
to  the  old  structure  and  extending  some  distance  below  it.  The 
trouble  is  to  avoid  settlement  of  the  old  work  while  this  is  going  on. 
In  material  not  full  of  water,  the  excavation  can  be  safely  accom- 
plished by  means  of  cases,  similar  to  those  used  in  military  mining, 
but  modified  according  to  circumstances.  If  the  excavation  seems 
too  dangerous,  piles  may  be  driven  at  the  points  where  the  ends  of 
needles  are  to  be  supported;  if  it  will  not  do  to  drive  them  with  an 
ordinary  ram,  they  can  be  screwed  in  or  sunk  with  a  water  jet.  There 
is  a  patented  method  of  supporting  an  old  wall  during  underpinning 
which  consists  in  cutting  slots  in  it,  setting  up  in  them  piles  made 
of  iron  pipe,  and  forcing  the  latter  down  with  jacks  working  between 
the  tops  of  the  piles  and  the  masonry  above.  This  operation  is  con- 
tinued until  it  is  evident  that  the  piles  are  able  to  carry  the  load  without 
further  settlement.  The  space  between  the  tops  of  the  piles  and  the 
masonry  can  be  filled  up  with  iron  blocks,  or  otherwise,  and  the  old 
foundation  taken  out.  The  piles  would  be  built  into  the  new  founda- 
tion. The  writer  can  not  refer  to  work  actually  done  by  this  method, 
nor  give  any  figures  of  cost.  But  it  seems  plausible  where  the  con- 
ditions are  otherwise  difficult  and  the  work  important.  The  cost 
would  probably  be  considerable.  Where  a  wall  is  supported  by  in- 
clined shores,  these  should  cut  into  it  at  points  not  far  from  girders 
and  floor  beams,  so  as  to  get  the  benefit  of  their  lateral  support.  If 
it  is  supported  on  needles,  it  is  sometimes  necessary  to  excavate  both 
inside  and  outside  to  get  support  for  the  needles  from  the  level  of  the 
new  foundation.  Sometimes,  by  using  a  long  needle  and  allowing 


19 

the  inner  end  to  rest  on  the  basement  floor  or  the  earth  inside  for 
some  distance  back  from  the  wall,  inside  excavations  can  be  avoided. 

Sometimes  it  is  necessary,  not  only  to  hold  a  vertical  weight,  but 
also  to  hold  a  bank  from  caving.  In  such  cases  great  care  is  required, 
but  no  general  rule  can  be  laid  down.  In  all  cases  of  underpinning, 
the  engineer  must  consider  not  only  what  his  temporary  supports  shall 
be,  but  how  he  will  get  them  in  place,  which  is  the  larger  half  of  the 
work. 

All  foundations  should  be  finished  with  a  -dampproof  course,  to 
prevent  moisture  from  rising  in  the  walls.  The  best  materials  for 
waterproofing  and  dampproofing  are  asphalted  wool  felfs  and  certain 
asphalts,  which  do  not  rot  in  the  presence  of  water.  Neuchatel  and 
Seyssel  Rock  Asphalt  mastics,  Alcatraz  or  Bermudez  asphalts  are  all 
reliable,  when  properly  applied.  Where  the  tops  of  foundations  are 
covered  with  dampproofing,  it  must  be  made  so  it  will  not  squeeze 
out  under  the  pressure.  Rock  asphalt  mastic  can  be  mixed  with  fine 
gravel  an'd  made  waterproof,  yet  hard  enough,  when  applied  in  very 
thin  layers,  to  withstand  heavy  crushing  loads.  On  vertical  surfaces 
and  in  the  body  of  concrete  floors,  it  is  better  to  use  the  felts  and 
swabbing  coats  of  asphaltic  cement,  either  hot  or  cold;  the  mastic 
might  crack  in  such  places,  as  it  is  quite  stiff  when  cold. 

Having  settled  the  question  of  foundations,  the  steelwork  is  in 
order.  The  columns  should  always  rest  on  bases  of  built-up  steel  or 
of  cast  steel  or  iron.  If  of  cast-iron,  no  part  should  be  less  than  1 
inch  thick;  an  inch  and  a  half  would  be  a  better  minimum.  Such  a 
base  should  never  be  shallow,  and  should  not  be  too  economically 
designed.  It  should  consist  essentially  of  top  and  bottom  bases,  con- 
nected by  ribs  running  in  both  directions  across  the  plates.  The 
sides  of  the  base  should  slope  at  angles  of  about  60°  with  the  hori- 
zontal— certainly  not  less  than  45°.  A  base  built  up  of  steel  can  be 
allowed  to  have  some  transverse  strain,  but  must  be  so  stiff  it  can  not 
suffer  appreciable  distortion.  Buildjng  up  an  efficient  steel  column 
base  is  not  so  simple  as  it  looks,  and  it  should  receive  the  careful 
attention  of  the  engineer  in  charge  of  the  work  in  every  case.  Like 
post  caps  and  joist  hangers,  a  built-up  column  base  must  be  carefully 
designed  in  all  of  its  parts,  to  resist  all  possible  local  strains. 

With  the  columns,  the  question  of  structural  steel  proper  is  reached. 
It  is  customary  to  use,  as  the  maximum  fiber  stress  on  structural  steel 
in  buildings,  16,000  pounds  per  square  inch.  In  the  case  of  the 
columns,  this  is  the  constant  that  is  put  into  the  column  formulae, 
and,  of  course,  the  actual  direct  stress  per  square  inch  is  considerably 


20 

less,  because  of  the  allowance  for  buckling.  If  the  column  is  properly 
fireproofed,  however,  it  will  be  stiff  enough,  without  any  allowance 
for  buckling.  It  is  better,  in  such  a  case,  to  design  it  in  simple 
compression — i.  e.,  divide  the  total  load  in  pounds  by  16,000,  and 
take  the  result  as  the  area  of  cross  section  of  the  column  in  square 
inches.  What  is  considered  proper  fireproofing  will  be  described' 
later.  In  cases  where  buckling  must  be  considered,  the  parabolic 
formula  given  in  Johnson's  Modern  Framed  Structures,  or  Gordon's 
formula,  should  be  used.  The  straight  line  formula  is  reliable  within 
certain  limits,  but  it  gives  loads  much  too  great  be}'ond  these  limits. 
In  considering  various  forms  of  column,  it  should  be  remembered  that 
often  the  entire  load  is  directly  applied  to  only  a  part  of  the  column, 
and  must  be  distributed  throughout  the  section  by  whatever  means 
have  been  adopted  for  tying  the  parts  of  the  section  together.  A 
good  test  of  a  column  design  is  to  consider  whether,  if  used  as  a 
girder,  in  any  position,  it  would  have  sufficient  strength  in  the  web 
members  to  develop  the  strength  of  the  flanges;  unless  it  has,  it  is 
not  an  ideal  design.  It  is  not  necessary  to  have  it  absolutely  ideal,  and  in 
most  cases  in  ordinary  practice  it  is  not.  There  should  be  a  fairly  close 
approximation  to  ideal  conditions,  however — and  judged  by  this  cri- 
terion there  are  a  number  of  column  sections — notably,  one  made  up  of 
angles  connected  at  intervals  by  short  batten  or  tie  plates — which  are 
wholly  bad,  and  should  never  be  used,  unless  they  can  be  entirely 
bedded  in  a  mass  of  concrete. 

An  ideal  column  section  considered  merely  from  its  capacity  to  resist 
compression  and  the  tendency  to  buckle  under  compression,  is  a 
hollow  circular  cylinder;  but  such  a  column  would  be  difficult  to 
splice  and  it  would  be  very  difficult  to  attach  beam  and  girder  brackets 
to  its  sides.  Every  practicable  column  section  is  a  compromise  between 
the  extremes  of  ideal  resistance  to  compression  and  buckling  under  a 
centrally  applied  load  on  the  one  hand,  and  of  facility  and  ease  of 
designing  and  applying  practicable  connections,  on  the  other.  Col- 
umns made  up  of  channels,  with  lattice  bars  or  cover  plates,  accord- 
ing to  the  load,  and  columns  of  I  section  built  of  plates  and  angles, 
or  of  an  I  beam  and  two  channels,  or  other  equivalent  shapes,  are 
among  the  best. 

Eccentric  loading  must  be  provided  for,  in  every  case.  The  best 
way  to  provide  for  it  is  to  eliminate  it,  even  at  some  expense,  and  at 
the  sacrifice  of  ideal  conditions  in  other  respects.  In  the  case  of  a  lat- 
ticed channel  column,  which  is  one  of  the  best  types,  if  there  is  a  load 
on  only  one  side  of  it,  a  seat  for  the  girder  or  beam  can  be  built  in 


21 

between  the  channels,  so  as  to  apply  the  load  on  the  axis.  Z-bar  col- 
umns, or  columns  of  I  section,  can  usually  be  set  so  that  unbalanced 
loads  can  be  applied  directly  to  the  webs,  thus  largely  eliminating 
eccentricity.  If  a  column  is  loaded  symmetrically,  even  though  the 
loads  are  all  applied  at  a  distance  from  its  axis,  it  is  quite  safe  to 
consider  the  total  load  as  centrally  applied.  In  this  case,  if,  in  the 
use  of  the  building,  the  live  load  should  be  in  place  on  one  side, 
but  not  on  the  other,  there  will  be  an  eccentric  load,  causing  trans- 
verse stress  in  the  column;  but  the  metal  put  in  to  carry  the  remain- 
ing live  load,  will  usually  take  care  of  this  bending  safely  enough, 
although  the  stresses  may  run  up  to  24,000  or  25,000  pounds  per 
square  inch.  Great  care  should  be  exercised  in  connecting  heavy 
girders  of  long  span  to  the  columns  that  carry  them. 

It  will  not  do  to  make  rigid  connections  in  such  cases,  for  the  normal 
deflection  of  the  girder  under  its  load  will  introduce  strains  in  the 
column  beyond  all  reasonable  limits.  If  the  span  of  the  girder  exceeds 
ten  times  its  depth,  or  if  it  is  greater  than  15  feet,  the  equation  of 
the  curve  of  mean  fiber — or,  at  any  rate,  its  first  differential  coefficient, 
should  be  deduced.  From  this  the  inclination  of  the  curve  of  mean 
fiber  at  the  points  of  support  can  be  determined.  Compute  the 
moment  of  inertia  of  the  column  section,  and  find  from  the  differen- 
tial equations  of  the  curve  of  mean  fiber,  what  uniform  bending 
moment  would  cause  the  curve  of  mean  fiber  to  take  an  inclination 
at  the  ends  at  right  angles  to  that  of  the  girder.  From  this  the  fiber 
stress  produced  by  the  bending  can  be  determined.  This  method  is 
only  approximate;  it  treats  the  columns  as  a  beam  resting  on  two 
points  of  support,  and  subjected  to  a  uniform  bending  moment.  As 
a  matter  of  fact,  the  column  is  generally  continuous  past  several  girder 
connections,  and  if  these  connections  are  rigid,  both  columns  and 
girders  are  partially  fixed  at  the  reaction  points.  However,  the 
approximation  will  always  be  on  the  side  of  safety,  and  if  it  indicates 
dangerous  stresses  in  the  column  from  the  deflection  of  the  girder, 
the  connection  should  be  so  designed  as  to  leave  the  girder  free  to 
deflect,  without  sliding  off.  This  will  generally  result  in  a  bracket 
riveted  to  the  column,  for  the  ends  of  the  girder  to  rest  upon.  It 
should  be  bolted  to  the  bracket,  to  prevent  all  danger  of  sliding  off. 

The  columns,  in  fireproof  buildings,  are  generally  made  continuous 
from  bottom  to  top.  If  the  increments  of  load  at  successive  floors 
are  very  great,  it  will  be  cheaper  to  splice  the  columns  at  every  floor; 
but  this  does  not  often  happen,  and  columns  are  generally  made  two 
or  three  stories  high.  .A  column  of  any  of  the  ordinary  types  can  be 


22 

made  and  kept  reasonably  straight  and  true  in  lengths  up  to  40  feet.  It 
is  better  to  reduce  the  number  of  splices  as  much  as  possible,  even  if 
the  column  weighs  a  little  more,  and  rather  high  stresses  have  to  be 
accepted  in  its  lower  part.  It  is  not  practicable  to  splice  columns  in 
buildings  with  full  splices,  as  in  the  case  of  compression  members  of 
bridges.  There  are  two  reasons  for  this:  one  is  that  the  splices 
would  be  very  awkward  to  design  and  execute,  and  the  other  is  that 
they  are.  very  expensive.  When  the  function  of  the  splice  plates  and 
angles  is  reduced  to  merely  holding  the  columns  in  line,  it  is  neces- 
sary that  the  column  ends  should  be  very  accurately  faced  off.  Just 
how  serious  a  matter  this  is  may  be  seen  from  a  discussion  by  the 
writer  in  Engineering  News,  December  25,  1902,  page  544.  It  is 
sufficient  here  to  say  that  to  realize  the  full  factor  of  safety  at  the 
column  splices  requires  a  grade  of  workmanship  not  always  easy  to 
obtain.  This  is  another  reason  for  making  as  few  splices  as  possible. 
Where  a  splice  is  to  be  made,  the  maximum  economy  of  metal 
would  place  it  just  at  the  point  where  the  full  section  of  the  lower 
column  is  first  required.  This  would  be  at  the  bottom  of  floor  gird- 
ers; further  consideration  would  point  to  a  location  at  the  middle 
of  the  depth  of  the  floor  girders,  so  that  the  ends  of  the  columns 
would  be  in  a  pocket  formed  by  girders  and  beams,  and  thus  secure 
a  certain  reinforcement  for  the  splice.  But  practical  experience  de- 
mands that  the  entire  splice  be  above  the  tops  of  girders  and  beams. 
This  makes  it  possible  to  complete  a  floor  of  beams  and  girders  with- 
out waiting  for  the  tier  of  columns  above.  When  the  upper  columns 
come,  they  can  be  placed  and  the  splices  riveted  up  without  the  use 
of  hanging  scaffolds,  which  is  in  itself  a  point  of  enough  importance 
to  more  than  counterbalance  any  saving  in  metal  effected  by  placing 
the  splice  lower  down.  The  column  bearing  can  be  more  readily  in- 
spected, and  the  work  on  the  splice,  being  more  accessible,  will  be 
better  done.  If  a  floor  of  beams  and  girders  is  not  complete  without 
the  upper  tier  of  columns,  a  multitude  of  details  of  other  work  will  be 
delayed  thereby,  and  this  again  is  in  itself  a  sufficient  reason  for 
locating  the  splice  as  herein  recommended. 

In  specifications  for  columns,  it  would  be  well  to  require  that  the 
ends  be  faced  off  true  to  within  1  per  cent.,  as  this  is  entirely  practi- 
cable; to  require  all  rivet  holes  in  splices  to  be  reamed  with  all  parts 
assembled  together,  or  else  drilled  to  a  steel  template;  all  holes  for 
connections  to  be  reamed  with  all  parts  assembled,  or  else  drilled  to 
steel  template.  These  requirements,  of  course,  are  in  addition  to  the 
standard  ones  as  to  rivet  spacing,  quality  of  steel,  etc.  The  inspector 


23 

at  the  mill  should  be  required  to  pay  especial  attention  to  these  points. 
If  they  are  properly  attended  to,  the  columns  can  be  designed  for  a 
minimum  stress  of  20,000  pounds  per  square  inch,  and  yet  be  safer 
than  current  practice,  based  on  16,000  pounds.  The  execution  in  the 
field  must  also  be  closely  watched  by  competent  inspectors.  It  is  well 
for  the  engineer  in  charge  himself  to  look  pretty  closely  after  field 
rivets  and  bolts  and  column  bearings.  The  writer  has  always  done 
this,  and  has  found  it  quite  necessary. 

In  the  upper  stories  of  buildings,  the  ordinary  splices  will  be  prac- 
tically full  splices,  because  of  light  column  loads.  In  such  cases,  if 
the  splice  rivets  are  properly  put  in,  it  is  a  matter  of  minor  import- 
ance for  the  columns  themselves  to  bear  accurately. 

In  all  construction  work,  however,  it  should  be  borne  in  mind  that 
execution  is  often  of  more  importance  than  design.  Good  execution 
will  often  save  a  poor  design,  but  no  excellence  in  design  can  make  a 
structure  proof  against  the  evils  of  poor  workmanship.  Yet  here 
again  the  young  engineer  must  remember  that  there  is  a  practical 
limit;  no  work  can  be  done  with  theoretical  accuracy,  and  it  often 
costs  enormously  to  make  a  very  close  approximation.  The  end  in  view 
should  be  the  required  factor  of  safety,  attained  beyond  all  doubt,  but  at 
the  least  total  expense  in  dollars  and  cents.  It  requires  judgment  to 
determine  the  economical  limit  between  mere  labor  and  mere  ma- 
terial; but  it  can  be  said  in  a  general  way  that  current  practice  in 
building  construction  is  lavish  of  material  and  parsimonious  in  labor 
and  supervision.  Better  results  could  be  achieved  for  less  money,  by 
sacrificing  part  of  the  material  and  increasing  the  standard  of  work- 
manship, within  reasonable  limits. 

Next  to  the  columns,  the  girders  are  the  most  vital  members  of  a 
steel  frame.  Little  can  be  added  to  the  chapter  on  the  plate  girder 
in  Johnson's  Modern  Framed  Structures.  A  plate  girder  for  a  build- 
ing should  always  be  designed  without  stiffeners  if  possible.  Stif- 
feners  form  pockets  between  the  flanges,  which  make  the  placing  of 
the  floor  beams  very  difficult  and  expensive  and  add  to  the  pound 
price  of  the  girder.  All  things  considered,  it  is  usually  cheaper  to 
put  more  metal  in  the  web  plate  and  do  away  with  the  stiffeners  ex- 
cept at  the  ends;  here  they  should  never  be  omitted.  All  rivet  holes 
in  a  plate  girder  should  be  punched  small  and  then  reamed  out  with 
all  parts  assembled.  Of  course,  holes  drilled  from  the  solid  to  a 
steel  template  would  be  ideal;  and  punched  holes  are  too  ragged  and 
match  too  poorly  to  be  tolerated  in  first-class  work.  But  the  drill- 
ing from  the  solid  is  too  expensive  in  the  present  state  of  the  art,  and 
the  method  recommended  is  probably  as  good  for  all  practical  pur- 


24 

poses.  Every  rivet  in  a  plate  girder  is  supposed  to  do  full  duty,  so 
that  both  the  holes  and  the  rivets  themselves  should  be  carefully 
watched.  It  is  in  points  of  this  kind  that  the  inspector  at  the  mill 
should  prove  his  worth;  he  should  never  relieve  the  contractors  from 
responsibility  for  correct  dimensions  and  fit  of  various  pieces,  and,  if 
necessary,  should  check  up  no  dimensions  at  all,  but  devote  his  whole 
time  to  .the  quality  of  the  work. 

If  rolled  beams  conform  to  the  usual  standard  specifications,  noth- 
ing further  will  be  required.  Wherever  possible,  they  should  transmit 
their  loads  to  girders  and  columns  through  single  heavy  angle  brack- 
ets without  stiffeners  beneath,  as  this  avoids  introducing  tensile  stress 
in  the  rivets  due  to  deflection  of  the  beam  and  the  concentration  of 
the  load  on  the  outer  edge  of  the  bracket.  The  idea  is  that  the  out- 
standing leg  of  the  angle  will  bend  and  accommodate  itself  to  the 
deflection  of  the  beam  and  thus  throw  the  load  close  in  to  the  web, 
where  it  will  produce  only  shearing  stresses  in  the  rivets. 

It  is  in  the  details  and  connections  that  the  structural  designer  has 
the  best  opportunity  to  show  his  skill.  These  make  up  quite  a  per- 
centage of  the  total  weight;  they  almost  never  fall  below  10  per  cent., 
and  often  go  as  high  as  20.  Cases  arise  more  frequently  in  buildings 
than  in  other  structural  work,  where  many  heavy  connections  have  to 
be  crowded  into  a  small  space.  These  often  demand  a  great  deal  of 
care  and  ingenuity  for  their  proper  solution. 

There  are  other  points  affecting  the  economy  of  the  design  in  a  steel- 
frame  building,  however.  If  columns  and  girders  can  be  so  placed 
that  a  girder  comes  over  a  partition,  it  will  often  be  possible  to  give 
it  the  full  economical  depth;  whereas,  in  another  location,  the  archi- 
tect might  object  to  so  great  a  projection  below  the  ceiling,  and  the 
girder  would  have  to  be  made  shallow,  regardless  of  economy. 

Long  spans  for  beams  and  girders  should  always  be  avoided  as  far 
as  possible.  It  is  much  cheaper  to  put  in  more  columns,  which  carry 
their  loads  by  direct  stress,  than  to  use  long  span  deep  girders.  The 
span  of  girder  should  not  exceed  20  feet,  unless  longer  spans  are  im- 
peratively demanded.  If  a  bay  of  the  floor  system  is  wider  in  one  di- 
rection than  the  other,  and  the  depth  of  the  girders  is  not  seriously 
limited,  it  will  usually  be  more  economical  to  run  the  girders  the  long 
way,  and  the  floor  beams  the  short  way. 

In  making  the  steel  plans  for  a  large  building,  the  columns  should 
first  be  marked  by  a  system  of  coordinates,  so  that  the  mark  of  the 
column  would  indicate  its  location.  The  different  stories  or  tiers 
would  be  indicated  by  prefixing  the  number  of  the  story  or  tier  to  the 


25 

mark  of  the  column.  Thus  if  a  corner  of  the  building  be  assumed 
as  an  origin  of  coordinates,  the  rows  of  columns  in  one  direction 
could  be  lettered,  and  in  the  other  numbered,  beginning  in  each  case  at 
the  origin — the  corner  column  here  being  1-A.  The  girders  can 
conveniently  be  designated  by  the  number  of  the  floor  and  the  marks 
of  the  columns  they  connect,  while  floor  beams  can  receive  the  number 
of  the  floor,  the  mark  of  the  bay,  and  their  serial  number  in  the  bay. 
By  this  means,  the  location  of  every  piece  can  be  determined  at  once 
by  its  marks.  The  make-up  of  columns  can  be  conveniently  indicated 
by  taking  a  large  sheet  and  ruling  it  in  parallel  vertical  columns. 
Each  of  these  should  receive  a  column  mark,  and  be  divided  into  a 
number  of  equal  lengths,  representing  the  stories.  The  make-up  of 
the  columns,  the  location  and  general  character  of  splices,  and  levels 
at  which  main  girders  are  connected,  can  all  be  written  and  otherwise 
indicated  in  the  spaces  thus  laid  out.  It  only  remains  then  to  make 
drawings  illustrating  typical  details  and  supplement  them  by  proper 
specifications. 

For  the  girders,  it  is  best  to  make  a  complete  drawing  for  each  type, 
though  small  variations,  covering  many  slightly  different  girders,  can 
be  indicated  on  a  single  type  drawing.  For  floor  beams,  it  is  sufficient 
to  indicate  their  size  and  weight  on  the  beam  plans,  and  to  illustrate 
their  connections  by  drawings.  The  beam  plan  should  show  column 
centers  by  means  of  crosses  or  circles,  and  centers  of  girders  or  beams 
by  straight  lines.  The  mark,  size,  weight,  etc.,  of  each  girder  or 
beam  should  be  indicated  on  this  plan. 

In  writing  specifications,  it  should  always  be  provided,  in  case  of  a 
very  large  building,  that  the  erector  must  provide  a  storage  place  apart 
from  the  building,  where  the  steel  can  be  delivered  and  sorted,  and 
then  brought  to  the  building  in  the  order  in  which  it  is-needed  for 
erection.  The  reason  for  this  is  that  it  is  never  economical  for  the 
mills  to  turn  the  material  out  in  this  order;  there  may  be  girders  in 
all  the  floors  exactly  alike;  there  are  sure  to  be  beams  that  are  uniform 
for  all  stories;  the  mills  will  usually  run  out  all  pieces  of  a  kind  to- 
gether. If  they  were  allowed  to  be  delivered  at  the  building,  the 
erection  of  the  lower  tiers  would  soon  be  stopped  by  the  congestion  of 
materials  intended  for  the  upper  ones. 

Better  prices  will  usually  be  obtained  if  the  specifications  provide 
for  partial  payments  on  steel  delivered  at  the  building,  but  not  fully 
erected  and  accepted.  To  prevent  the  contractor  from  taking  undue 
advantage  of  this,  steel  delivered  at  the  storage  yard  and  not  needed 


26 

for  immediate  erection  should  not  be  allowed  at  the  building,  nor 
paid  for,  until  it  is  brought  in,  in  due  course. 

To  protect  the  steel  from  corrosion  during  transporation  and  erec- 
tion, it  should  receive  a  coat  of  paint  or  linseed  oil  before  shipment. 
The  best  results  would  be  attained  by  thorough  cleansing  of  the  steel 
in  an  acid  bath  or  by  the  sand  blast,  or  both,  and  the  immediate  ap- 
plication of  the  paint  to  fresh  and  perfectly  clean  surfaces.  All  trace 
of  acid  and  of  the  lubricating  oil  smeared  on  during  handling  and 
manufacturing  should  be  cleaned  off  before  painting.  As  a  matter  of 
fact,  no  shop  is  equipped  for  treating  structural  steel  in  so  elaborate 
a  way.  It  ought  to  be  done,  nevertheless,  for  bridges  and  viaducts, 
but  it  is  not  necessary  for  buildings,  if  proper  precautions  are  ob- 
served. If  the  durability  of  the  steel  in  a  building  really  depended 
on  the  paint,  the  average  life  of  a  steel-frame  building  would  hardly 
exceed  twenty-five  years.  In  practice,  however,  all  the  steel  members 
are  more  or  less  thoroughly  covered  with  Portland  cement  masonry, 
and  this  is  the  real  protection.  If  it  is  carried  to  its  logical  conclu- 
sion, so  as  to  secure  complete  covering  and  perfect  contact  through- 
out, the  life  of  the  steel  will  be  indefinite;  this  will  be  true,  even  if 
the  steel  is  red  with  rust  when  built  in,  provided  scales  have  not  be- 
gun to  form.  It  may  stop  the  corrosion  and  suspend  it  indefinitely, 
even  in  the  latter  case.  For  a  discussion  of  the  writer's  views  on  this 
subject,  reference  is  made  to  an  article  published  in  Engineering 
News  of  October  23,  1902,  under  the  title  of  "Columns  for  Build- 
ings." It  is  sufficient  here  to  say  that  the  corrosion  of  steel  or  iron 
requires  the  simultaneous  presence  of  an  acid,  moisture,  and  oxygen. 
A  limited  amount  of  acid,  with  an  indefinite  supply  of  moisture  and 
oxygen,  will  ultimately  corrode  a  large  amount  of  steel.  Portland 
cement  in  contact  with  steel  protects  it,  because  it  is  alkaline  and  has 
a  stronger  affinity  for  acids  than  iron  has;  it  therefore  neutralizes  any 
acid  before  it  can  attack  the  steel.  Under  the  conditions  existing  in 
buildings,  there  is  enough  Portland  cement  around  the  steel,  if  the 
latter  is  completely  imbedded,  to  neutralize  all  the  acid  that  is  likely 
to  be  absorbed  by  the  covering  for  hundreds  of  years.  If,  however, 
the  masonry  is  built  around  the  steel,  leaving  hollow  spaces,  and  if  it 
cracks  or  has  unfilled  joints,  allowing  circulation  of  the  air,  the 
moisture  and  acid  mav  reach  the  steel  without  being  filtered  through 
the  masonry,  and  in  that  case,  corrosion  may  proceed  at  a  serious 
rate.  For  the  best  results,  all  the  steel  should  be  in  close  contact 
with  Portland  cement  mortar  over  all  parts  of  its  surface. 

Closely  related  to  the  protection  of  steel  from  corrosion   is  its  pro- 


27 

tection  from  fire.  The  first  iron  that  was  used  for  columns  and 
beams  in  buildings  was  introduced  with  the  idea  that  it  would  be 
fireproof.  This  turned  out  to  be  an  erroneous  idea;  but,  in  modern 
high  buildings  there  is  the  additional  reason  for  the  use  of  iron  or 
steel,  that,  up  to  the  present,  at  any  rate,  no  other  material  has  been 
found  strong  enough  to  carry  the  heavy  loads  without  cross-sections 
so  large  that  the  floor  space  in  the  lower  stories  would  be  seriously 
diminished.  This  consideration  was  what  led  to  carrying  the  walls 
of  a  building  as  well  as  the  floors  on  the  steel  frame.  No  wall  be- 
ing more  than  one  story  high,  it  was  possible  to  make  all  of  them  of 
a  minimum  thickness,  and  reduce  them  to  a  mere  curtain  for  keeping 
out  the  weather. 

It  is  vitally  important  for  a  high  building  to  be  fireproof;  all 
Government  structures  of  any  prominence  should  be  fireproof.  It  is 
well  then  to  inquire  what  a  fireproof  building  is,  and  in  what  its 
fireproof  character  consists. 

A  building  is  entitled  to  be  called  fireproof  only  when  it  is  able  to 
stand  an  ordinary  fierce  conflagration  without  damage,  except  to 
paint,  plaster,  glass,  and  wooden  floor  finish,  if  there  is  any.  This 
damage  repaired,  the  building  must  be  able  to  come  through  a  sec- 
ond— indeed  many,  similar  ordeals.  Making  a  building  fireproof  will 
not  make  its  contents  incombustible,  so  that  quite  fierce  fires  may 
occur  in  fireproof  buildings;  but,  although  the  damage  to  the  con- 
tents may  be  100  per  cent.,  that  to  the  buildings  should  not  exceed 
5  or  6  per  cent.,  if  it  is  really  fireproof. 

To  be  fireproof,  a  structure  must  be  incombustible  and  infusible, 
and  must  retain  its  form  and  strength  unimpaired  at  any  tempera- 
ture possible  in  a  fire;  temperatures  in  a  conflagration  rarely  exceed 
2,500°  F.,  although  wrought-iron  has  been  known  to  melt  in  spots, 
which  would  indicate  local  temperatures  as  high  as  3,000°  F. 

Steel  and  cast-iron  are  incombustible,  but  not  fireproof.  At  com- 
paratively low  temperatures  they  lose  their  rigidity  and  are  bent  and 
twisted  in  every  conceivable  way.  When  this  happens,  the  floors  are 
destroyed,  the  contents  of  the  building  are  precipitated  to  the  ground, 
the  expansion  of  the  steel  often  throws  the  walls,  and  the  wreck  is 
worse  than  if  the  floors  and  columns  had  been  entirely  of  timber. 

The  fireproof  problem  generally  consists  in  devising  a  covering  for 
steel  and  iron  which  will  protect  the  steel  from  high  temperatures, 
resist  the  fire  itself,  and  have  sufficient  strength  to  resist  ordinary 
wear  and  tear.  This  covering  is  nearly  always  some  form  of  masonry. 

Very  few  natural  stones  can  resist  high  temperatures.      Limestones 


28 

and  marbles  are  destroyed  by  driving  off  the  C  O2;  all  stones  crack 
and  fly  to  pieces,  except  some  rare  forms  of  sandstone,  when  exposed 
to  high  temperatures.  While  stones  are  incombustible  they  are  not 
fireproof. 

The  various  forms  of  burned  clay  all  have  more  or  less  power  to  re- 
sist heat.  They  have  all  been  subjected  to  fairly  high  temperatures 
in  burning,  and  they  are  all  relatively  poor  conductors  of  heat,  which 
is  essential  if  the  steel  is  to  be  prevented  from  attaining  a  high  tem- 
perature. Dense,  hard  burned  clay,  however,  when  subjected  to  the 
sudden  changes  of  temperature,  is  very  liable  to  crack,  although  it 
does  not  fly  to  pieces  as  stone  does.  In  the  kiln  it  is  subjected  to 
very  great  changes  of  temperature,  but  they  are  very  gradual.  When 
used  for  fireproofing,  clay  products  are  generally  known  as  terra  cotta. 
By  this  name  they  will  be  called  hereafter.  The  clay  used  for  terra 
cotta  fireproofing  should  be  strong  and  tough,  and  should  not  melt  at 
temperatures  less  than  3,000°  F.  It  should  be  thoroughly  burned,  and 
should  require  a  temperature  of  at  least  2,300°  to  2,500°  F.  to  accom- 
plish this.  It  is  much  more  efficient  both  as  a  non-conductor  and  in 
resisting  strains  due  to  sudden  changes  of  temperature  if  as  large  a 
proportion  of  sawdust  as  possible  is  mixed  with  it  before  burning. 
This  produces  what  is  known  as  porous  terra  cotta.  If  burned  hard 
enough  for  the  highest  efficiency,  it  can  not  be  cut  with  a  saw  and 
will  not  hold  nails,  as  is  often  claimed  for  it.  Even  the  softer  grades 
commonly  used  can  not  be  depended  upon  in  this  respect,  the  state- 
ments in  the  maker's  catalogues  to  the  contrary  notwithstanding. 
Selected  pieces  can  always  be  found  of  which  it  is  true,  but  no  large 
deliveries  will  contain  a  sufficient  percentage  of  such  pieces  to  be 
depended  upon. 

No  fireproof  material  is  superior  to  the  best  grades  of  porous  terra 
cotta,  when  it  is  properly  applied.  In  the  form  of  the  hollow  blocks 
ordinarily  found -in  the  market,  however,  it  is  merely  fire-resisting,  not 
fireproof.  These  blocks  have  very  thin  webs;  when  exposed  to  the 
fire,  they  very  quickly  become  heated  through.  They  are  backed  by 
dead  air  spaces,  and  are  joined  at  the  corners  of  the  blocks  to  other 
thin  webs  not  exposed  to  the  fire.  The  result  is  very  serious  strains 
due  to  unequal  heating  of  the  block  as  a  whole,  with  comparatively 
sudden  transition  from  the  hot  to  the  cold  parts.  This  alone  will 
cause  the  outer  webs  to  crack  and  fall  off  in  a  hot  fire,  and  the  appli- 
cation of  cold  water  from  a  fire  hose  brings  this  about  at  once.  The 
hollow  tiles  were  developed  with  a  view  to  lightness,  and  with  the 
idea  that  the  dead  air  spaces  would  increase  the  protection  from  fire. 


29 

The  latter  is  a  fallacy;  the  effects  of  unequal  distribution  of  heat 
were  not  foreseen  and  do  not  seem  to  be  fully  realized  yet.  Two 
fires  in  a  store  building,  known  as  the  Home  Store,  in  Pittsburg,  in 
the  years  1897  and  1900,  illustrated  this  weakness  of  hollow  tile  very 
well.  These  fires  will  be  found  described  in  the  Engineering  Record 
of  May  22,  June  26,  and  July  17,  1897,  and  of  April  14, 1900.  Hollow 
tiles  present  two  or  more  parallel  webs  of  thin  section,  separated  by 
dead  air  space,  when  in  place.  To  expect  those  to  successfully  resist 
a  fierce  fire,  is  like  holding  a  military  position  with  a  series  of  thin 
skirmish  lines,  the  most  advanced  of  which  occupies  the  key  to  the 
whole  position.  When  it  is  known  beforehand  what  the  exact  loca- 
tion of  the  supreme  trial  of  strength  is  to  be,  it  follows  that  there 
should  be  concentrated  the  full  strength  of  the  defense.  This  is  as 
true  of  fireproofing  as  of  a  battle.  When  the  outer  webs  are  broken 
off,  the  hollow  blocks  themselves  are  a  total  loss,  even  though  they 
may  still  protect  the  steel  with  more  or  less  success.  What  is  true  in 
this  respect  of  porous  terra  cotta  is  doubly  true  of  the  dense  variety. 

To  make  hollow  blocks  really  fireproof,  the  webs  should  be  2  inches 
thick.  The  material  can  not  be  successfully  and  economically  burned 
in  greater  thickness  than  this,  or  it  would  be  desirable  to  make  it 
greater. 

A  better  form  of  fireproofing  would  be  4  inches  of  brickwork,  in 
which  the  bricks  were  made  solid  of  porous  terra  cotta.  But  where 
flat  ceilings  are  required,  flat  floor  arches  of  hollow  blocks,  with  webs 
2  inches  thick,  can  be  safely  used.  They  will  not  be  found  in  stock, 
but  must  be  made  to  order.  The  reason  the  thicker  webs,  or  the 
solid  bricks,  are  more  successful  in  resisting  fire  is  that  there  is  a 
greater  thickness  of  homogeneous  material,  and  the  change  of  tem- 
perature from  hot  to  cold  is  gradual.  The  resulting  strains  do  not 
exceed  the  strength  of  the  material  at  any  point.  Of  course,  the 
thicker  webs  make  heavier  blocks,  and  this  requires  more  steel  to  carry 
the  dead  load.  Herein  lies  one  reason  for  the  continued  use  of 
blocks  too  light  to  be  efficient  for  fireproofing.  Another  is  the  in- 
creased cost  of  the  heavier  blocks  themselves. 

Flat  floor  arches  are  almost  always  made  with  parallel  joints,  from 
motives  of  economy  in  manufacture;  it  reduces  the  number  of  sepa- 
rate patterns  required  and  makes  it  easier  to  allow  for  accidental  varia- 
tions in  the  spacing  of  floor  beams.  While  parallel  joints  seem  all 
wrong,  from  a  theoretical  point  of  view,  in  practice  they  are  all 
right.  Flat  side  construction  hollow  tile  arches  almost  invariably 
fail  bv  shearing  the  webs  of  the  blocks  nearest  the  beams — i.  e.,  in 


30 

the  skewbacks;  so  the  joints  are  stronger  than  the  blocks.  End  con- 
struction arches,  with  thin  webs,  are  very  difficult  to  set  properly,  be- 
cause of  the  small  area  of  end  section  available  for  receiving  the 
mortar.  In  these  blocks  the  joints  may  be  the  weakest  part  and 
should  be  carefully  looked  after.  If  webs  were  made  2  inches  thick^ 
this  trouble  would  be  largely  obviated.  Conditions  would  be  still 
further  improved  by  inserting  thin  continuous  slabs  in  the  joints,  but 
this  is  never  done,  except  to  make  up  for  accidental  variations  in  the 
spacing  of  beams. 

No  matter  what  kind  of  floor  arch  is  used,  the  lower  flanges  of  the 
beams  should  be  protected  with  at  least  2  inches  of  fireproof  material. 
The  best  method  of  doing  this,  probably,  is  with  a  heavy  protecting 
skewback  of  the  same  material  as  the  arches.  Metal  laths  and  plaster 
will  not  do;  the  fire  will  strip  them  off  in  ten  or  twelve  minutes,  and 
if  the  fire  does  not  the  water  will.  In  the  case  of  a  protecting  skew- 
back,  the  design  must  be  such  that  the  pressure  of  the  arch,  under  its 
load,  will  not  tend  to  break  off  the  protecting  flange.  This  will  have 
quite  enough  to  do  if  it  stays  in  place  under  the  action  of  fire  and 
water. 

For  the  protection  of  girders,  heavy  shoes  should  be  made  in  two 
pieces  to  fit  over  the  lower  flange ;  even  at  some  extra  expense,  the  th  ick- 
ness  of  the  material  in  these  shoes  should  be  made  at  least  2%  inches. 
The  shoe  should  be  filled  with  Portland  cement  mortar  and  squeezed 
into  place;  as  soon  as  the  cement  is  sufficiently  set,  the  web  covering 
should  be  built  up  on  either  side.  The  best  form  of  this  is  4  inches 
of  porous  terra  cotta  brickwork.  It  is  somewhat  heavy,  of  course, 
but  when  completed  it  possesses  considerable  transverse  strength, 
and  will  transmit  a  part  of  its  own  weight  to  the  columns.  Instead 
of  4  inches  of  solid  brickwork,  the  side  covering  might  be  built  of 
hollow  blocks  with  webs  at  least  2  inches  thick;  but  the  weight 
would  be  the  same,  and  the  solid  brickwork  is  more  efficient. 

Columns  should  always  be  covered  with  4  inches  of  solid  brickwork 
and  all  interior  spaces  filled  with  Portland  cement  concrete.  It  has 
been  repeatedly  demonstrated  that  4  inches  of  brickwork  will  protect 
steel  in  any  ordinary  conflagration,  and  if  it  is  sufficiently  tough  and 
refractory  itself  it  will  be  good  for  many  fires,  instead  of  only  one. 
Porous  terra  cotta  should  be  used  because  it  is  a  poor  conductor,  and 
is  able  to  take  up  contraction  and  expansion  within  itself  without 
developing  cracks.  It  should  be  hard  burned  to  enable  it  to  stand 
mechanical  shocks,  to  which  it  is  sure  to  be  subjected  in  practice, 
and  it  should  be  highly  refractory  to  prevent  it  from  melting.  It 


31 

would  be  well  to  specify  that  porous  terra  cotta  for  fireproofing  should 
be  made  of  tough,  refractory  clay,  with  at  least  20  per  cent,  of  its 
volume  of  sawdust  mixed  with  it  before  molding.  That  it  should  be 
burned  almost  to  vitrification,  and  must  be  able  to  stand  a  temperature 
of  at  least  2,800°  F.  without  melting  or  running.  These  specifica- 
tions can  be  complied  with  at  a  small  extra  cost  as  compared  with  the 
materials  commonly  used.  The  extra  cost  should  not  exceed  one-sixth. 
The  result  in  the  work  will  be  better  by  100  per  cent.  The  same 
grade  of  materials  should  be  used  for  floor  arches,  and  for  column  and 
girder  coverings.  If  flat  ceilings  are  not  required,  a  segmental  arch 
of  the  solid  porous  terra  cotta  bricks,  with  heavy  protecting  skewbacks, 
can  not  be  excelled.  To  secure  a  flat  ceiling  with  these  floor  arches 
would  require  metal  lathing  to  be  stretched  under  them,  at  an  extra 
cost  of  5  or  6  cents  per  square  foot  of  floor.  The  floor  arches  them- 
selves ought  not  to  cost  more  than  25  cents  to  27  cents  per  square  foot  of 
floor.  In  considering  the  relative  importance  of  different  parts  of  the 
fireproofing,  it  should  be  remembered  that  the  failure  of  a  single  floor 
arch  or  floor  beam  is  a  comparatively  small  matter;  the  failure  of  a 
girder  is  more  serious,  and  that  of  a  column  is  a  catastrophe.  Accord- 
ingly, the  column  protection  should  be  the  first,  the  girder  covering 
next,  and  the  floor  system  last,  in  power  of  resistance,  if  there  is  any 
difference.  In  current  practice,  this  order  is  just  reversed;  in  the  forms 
recommended  herein,  it  is  realized.  The  column  and  girder  coverings 
recommended  will  cost  at  least  twice  as  much  as  those  in  common 
use,  but  the  expenditure  is  fully  justified  by  the  results. 

In  the  case  of  the  columns,  they  will  be  so  greatly  stiffened  by  the 
covering  and  concrete  filling  that  they  can  be  safely  designed  without 
reference  to  buckling  in  simple  compression.  This  will  enable 
enough  steel  to  be  saved  to  more  than  pay  for  the  extra  cost  of  the 
covering,  and  the  completed  column  will  be  both  cheaper  and  better 
than  those  used  in  current  practice,  with  their  flimsy  hollow  tile 
covering. 

Next  to  porous  terra  cotta,  concrete  is  the  best  material  for  fireproof 
purposes.  When  made  with  Portland  cement,  it  will  withstand  very 
high  temperatures  without  material  injury.  The  best  concrete  for 
resisting  fire  is  made  of  Portland  cement,  sand,  and  the  ash  and  clinker 
from  steam  boilers  in  large  power  plants.  Domestic  ashes  and  ashes 
from  small  plants  are  apt  to  contain  a  good  deal  of  unburned  coal, 
which  always  has  sulphur  in  it;  this  is  liable  to  corrode  the  steel. 
Where  the  coal  is  entirely  burned,  however,  practically  all  of  the  sul- 
phur goes  off  with  the  volatile  products  of  combustion,  and  the  ashes 


32 

left  behind  will  not  corrode  iron.  Cinders,  like  locomotive  cinders, 
which  consist  practically  of  bits  of  coke,  are  combustible  and  corrosive ; 
they  never  give  a  good  bond  with  cement,  sd  they  make  a  very  weak 
concrete.  They  should  never  be  used.  There  are  cases  on  record 
where  concrete  made  of  them  has  been  subjected  to  the  heat  of  a  fire, 
and  has  slowly  burned  up. 

Concrete,  made  with  broken  stone,  when  subjected  to  heat,  cracks 
and  flakes  off  to  some  extent,  just  as  the  stone  itself  does.  Gravel 
concrete  stands  heat  better,  and  seems  to  give  greater  strength  when 
reinforced  with  steel  bars  than  stone  under  like  conditions.  Broken 
brick  gives  a  concrete  stronger  than  that  obtainable  from  ashes  and 
clinker,  and  probably  stands  fire  just  as  well.  Furnace  slag  is  said  to 
give  a  good  fireproof  concrete  when  broken  and  used  in  the  same  way 
as  gravel  or  broken  stone.  There  is  likely  to  be  some  sulphur  in 
furnace  slag  in  a  dangerous  form,  especially  if  the  slag  is  finely 
divided.  If  slag  is  to  be  used,  it  would  be  well  to  screen  out  all 
crusher  dust  and  wash  the  slag,  so  as  to  have  all  pieces  clean  and  not 
smaller  than  a  pea.  Under  these  conditions,  the  sulphur  is  not  likely 
to  be  very  active.  Portland  cement  clinker  and  neat  Portland  cement 
made  into  concrete,  make  a  product  that  can  not  be  excelled  for  fire- 
resisting  properties.  Many  cement  mills  mold  their  kiln  linings  from 
such  a  mixture,  and  find  it  superior  to  the  best  fire  bricks.  This  ma- 
terial, however,  is  not  generally  available  for  fireproof  work.  Port- 
land cement  is  burned  at  temperatures  probably  as  high  as  3,500°  to 
4,000°  F.,  so  the  clinker  has  passed  through  a  more  than  ordinary 
severe  test  in  the  process  of  manufacture.  The  only  weak  point 
about  Portland  cement  concrete  is  the  fact  that  water  has  been  added 
to  it  and  taken  up  in  the  process  of  setting.  This  water  can  prob- 
ably be  driven  off,  in  large  part  at  least,  by  the  application  of  heat. 
But  it  is  possible  that  the  cement  is  to  some  extent  re-clinkered  by 
this;  if  so,  the  concrete  ought  not  to  suffer  serious  diminution  of 
strength.  Practical  tests  show  that,  as  a  matter  of  fact,  it  does  not; 
whether  this  is  due  to  re-clinkering,  is  another  question.  A  fierce 
fire  will  probably  damage  stone  or  gravel  concrete,  and  possibly  brick 
and  cinder  concretes,  to  a  depth  of  about  three-fourths  of  an  inch,  so 
that  the  damaged  layer  will  either  come  off  or  have  to  be  taken  off. 
It  would  be  well,  in  using  concrete  for  fireproofing,  to  add  about  an 
inch  extra  thickness  all  around;  then,  in  the  event  of  a  fire,  the 
damaged  concrete  could  be  cleaned  off  and  its  place  supplied  by  metal 
lath  well  fastened  on  and  plastered  with  Portland  cement  mortar. 


33 

This  would  probably  prevent  the  damage  in  a  second  fire  from  pro- 
ceeding farther  than  that  due  to  the  first. 

In  using  concrete  for  fire  protection,  the  minimum  thickness  should 
be  about  the  same  as  for  terra  cotta,  and  all  column  and  girder  cover- 
ings should  have  a  skeleton  of  light  metal  shapes  to  hold  them  to- 
gether and  give  them  tensile  strength. 

Within  recent  years  concrete,  reinforced  with  steel  bars,  has  been 
much  used  under  transverse  stress.  It  is  used  in  flat  slabs  between  I 
beams,  instead  of  floor  arches.  In  some  cases,  it  is  used  as  an  arch 
proper,  built  on  a  wire  lath  center;  but  in  this  case  it  is  considered 
as  an  arch,  pure  and  simple.  The  metal  is  not  counted  on  to  fur- 
nish any  part  of  its  strength.  But  beams,  girders,  and  columns  are 
also  built  now  of  reinforced  concrete  with  entire  success.  Frames 
of  buildings  have  been  built  of  it  in  Europe,  similar  to  the  steel 
frames  used  here,  only  on  a  smaller  scale.  It  seems  destined  to  play  a 
most  important  part  in  the  structural  work  of  the  future.  It  would  not 
be  surprising  if  it  should  ultimately  drive  out  steel-frame  construction 
altogether.  Where  it  can  be  suitably  used  it  probably  yields,  con- 
sidering its  cost,  a  greater  return  in  the  way  of  durability,  strength, 
and  fireproof  qualities  combined  than  any  other  form  of  construction. 
It  is  designed  on  the  assumption  that  the  concrete  in  the  upper  part 
of  a  beam,  girder,  or  floor  plate  takes  all  the  compressive  stress,  while 
the  tensile  stress  in  the  lower  part  is  taken  entirely  by  the  steel  rein- 
forcement, or  partly  by  the  steel  and  partly  by  the  concrete.  A  great 
many  formulae  have  been  worked  out  for  the  design  of  reinforced 
concrete  beams  under  flexure.  They  are  all  based  on  the  ordinary 
theory  of  flexure,  modified  to  suit  the  circumstances  and  the  indi- 
vidual views  of  the  author.  Probably  as  convenient  a  set  of  working 
formulae  as  any  can  be  found  in  the  latest  catalogue  of  the  St.  Louis 
Expanded  Metal  Company,  which  contains  a  discussion  of  the  subject 
by  Mr.  A.  L.  Johnson,  Member  American  Society  of  Civil  Engineers. 
It  is  probable  that  his  formulae  are  as  reliable  as  any  others  available  at 
the  present  time.  It  should  be  stated,  however,  that  the  writer  has 
not  been  able,  so  far,  to  verify  equation  23,  on  page  58,  and  of  course 
this  applies  to  all  the  subsequent  equations  depending  upon  it.  Only  a 
very  little  time  has  been  spent  upon  equation  23,  and  it  is  quite  pos- 
sible that  it  is  correct.  Another  equation  in  this  catalogue  that 
seems  to  be  wrong  is  No.  39,  page  62.  The  writer  thinks  this 

i_      i  j  i_     o     ic  cos  v/  sin  *J 

should  be  o  = • 

2 

A  word  might  be  said  here  as  to  the  value  of  catalogues  as  sources 


34 

of  professional  information.  Along  with  the  technical  periodicals, 
and  transactions  of  the  Engineering  Societies,  they  constitute  the 
most  valuable  and  indispensable  part  of  an  engineer's  library.  A 
treatise,  setting  forth  the  fundamental  principles  of  any  branch  of 
engineering,  is  useful  as  the  first  step.  But  so  far  as  the  details  of 
practice  go,  it  is  out  of  date  before  it  is  printed,  and  the  engineer 
who  wishes  to  be  abreast  of  the  times  must  derive  his  information 
from  current  literature  and  the  practice  of  leading  contractors  and 
manufacturers.  It  should  be  remembered  that,  more  and  more, 
contracting  work  and  industrial  processes  are  passing  into  the  con- 
trol of  trained  engineers.  These  engineers  supply  the  information 
that  goes  into  the  catalogues.  They  are  generally  honest  men  and 
state  what  they  really  think;  they  would  not  dare  to  make  seriously 
inaccurate  statements  of  a  technical  nature;  they  are  in  a  better 
position  than  any  other  men  to  get  accurate  knowledge  ot  the  details 
of  their  specialties;  and,  as  a  matter  of  fact,  on  many  branches  of 
engineering,  the  catalogues  of  certain  large  concerns  are  the  best 
and  most  reliable  source  of  information.  The  fact  that  it  is  coupled 
with  advertising  matter  should  not  be  allowed  to  belittle  the  value  of 
the  information  they  contain. 

Probably  the  best  work  on  reinforced  concrete  is  "Beton  Arme, '* 
by  M.  Christophe.  No  thoroughly  satisfactory  work  is  printed  in 
English,  but  a  series  of  articles  descriptive  of  the  experiments  of 
M.  Considere  on  hooped  concrete  has  been  published  in  recent  numbers 
of  the  Engineering  Record,  and  should  be  read  by  every  one  interested 
in  the  design  of  reinforced  concrete  columns. 

In  addition  to  terra  cotta  and  concrete,  plaster  of  paris  has  been 
extensively  used  for  fireproofing.  But  this  substance  rapidly  deterio- 
rates under  fire  and  water,  is  mechanically  frail,  and  should  not  be 
used,  as  a  general  thing,  in  important  buildings.  There  are  circum- 
stances under  which  it  is  suitable,  but  there  is  not  space  to  go  into 
this  subject  here.  The  writer  would  have  been  glad,  indeed,  to  go 
more  extensively  into  the  whole  subject  of  fireproof  construction,  for 
in  no  other  part  of  a  building  is  there  more  need  of  an  engineer's 
special  training  and  in  none  is  the  lack  of  the  engineer's  work  more 
glaringly  apparent;  but  the  limitations  of  time  and  space  prevent  a 
full  discussion,  and  other  points  must  be  touched  upon. 

HEATING   AND  VENTILATION 

Most  modern  buildings  are  heated,  in  some  way,  by  either  steam 
or  hot  water.  If  radiators  are  placed  in  the  rooms  to  be  heated,  the 


35 

system  is  called  direct;  if  they  are  placed  in  the  basement  and  used 
to  heat  air  which  is  forced  over  them  and  through  hot-air  flues  into 
the  rooms,  the  system  is  called  indirect.  If  the  radiators  are  placed 
under  windows,  with  provision  for  the  admission  of  fresh  air  over 
their  heated  surfaces  through  openings  under  the  window  sills,  the 
system  is  known  as  the  direct-indirect.  In  any  of  these  systems, 
either  steam  or  hot  water  may  be  used.  If  a  blower  is  used  to  insure 
the  movement  of  air  over  indirect  radiation,  it  is  called  a  plenun  sys- 
tem; if  an  exhaust  fan  is  used  it  is  a  vacuum  system.  The  latter  is 
almost  never  used  in  indirect  heating,  however,  as  it  is  not  as  reliable 
as  the  other.  All  the  necessary  details  and  calculations  for  a  steam- 
heating  plant  can  be  found  in  "Baldwin  on  Heating,"  and  in  a  book 
on  the  same  subject  by  Prof.  R.  C.  Carpenter.  "Hot  Water  Heating 
and  Fitting"  is  the  title  of  another  work  by  Baldwin,  which  is  a 
standard  on  the  subject. 

A  steam-heating  system  consists  of  a  boiler  to  evaporate  the  water, 
supply  pipes  forcarrying  the  steam  to  the  radiators,  radiators  forcondens- 
ing  and  making  available  its  latent  heat,  and  return  pipes  forcarrying 
the  condensation  back  to  the  boiler.  The  supply  and  return  pipes  are 
sometimes  combined  in  one  set,  giving  a  "one  pipe"  system.  This 
is  suitable  only  for  small  plants.  In  all  such  cases,  the  condensed 
water  falls  back  through  the  rising  steam,  and  the  pipes  must  be  made 
large  enough  to  permit- of  this  without  interfering  with  the  necessary 
supply  of  steam.  In  the  case  of  steam  heaters,  a  damper  regulator, 
consisting  of  a  diaphragm,  weighted  on  one  side,  and  subjected  to 
the  steam  pressure  on  the  other,  can  be  very  advantageously  used  for 
automatic  regulation.  As  the  steam  pressure  rises  above  a  certain 
point,  it  raises  the  arm  carrying  the  weight,  and  by  means  of  a  chain 
connection  closes,  or  partly  closes,  the  damper  supplying  air  to  the 
fire  or  regulating  the  draft.  By  shifting  the  weight  the  pressure  in 
the  system  may  be  changed  from  day  to  day,  according  to  the  temper- 
ature. For  small  plants,  this  is  a  great  convenience, "and  enables  the 
plant  to  get  along  quite  satisfactorily  with  only  occasional  attention. 
No  other  system  of  heating  admits  of  automatic  regulation  in  50 
simple  and  direct  a  way. 

In  tall  buildings  it  is  customary  to  take  the  main  supply  pipe 
direct  to  the  top  of  the  building,  and  then  distribute  downwards. 
This  gives  much  more  positive  results,  and  may  be  said  now  to  be 
the  general  practice.  Ordinarily,  where  low  pressure  steam  is  used, 
some  sort  of  air  valve  is  put  on  the  radiators  to  enable  them  to  expel 
the  air;  otherwise  the  radiators  will  remain  cold,  as  the  steam  will 


36 

be  unable  to  fill  them.  Air  valves  generally  act  -by  the  unequal 
expansion  of  two  metals.  Many  of  them  are  quite  reliable,  if  properly 
placed  on  the  radiators. 

In  large  installations,  however,  it  is  often  the  case  that  a  vacuum 
pump  is  placed  on  the  returns.  This  speedily  empties  the  entire 
system  of  air,  and  increases  the  effective  pressure  of  the  steam  by 
creating  a  vacuum  in  front  of  it.  The  supply  pipes  can  be  made 
much  smaller  than  where  the  steam  and  condensation  are  expected  to 
circulate  under  gravity  and  low  pressure  alone.  Up  to  the  present, 
no  book  on  the  subject  has  treated  this  phase  of  the  subject  with 
thoroughness,  and  information  concerning  it  can  be  obtained  only 
through  the  current  publications,  and  from  people  controlling  certain 
patents  in  reference  to  it.  Steam  has  the  advantage  in  climates  sub- 
ject to  sudden  changes,  that  heat  can  be  obtained  quickly,  and  gotten 
rid  of  quickly,  since  the  weight  of  water  required  to  fill  the  system 
with  steam  is  comparatively  small. 

A  hot-water  plant  includes  a  heater,  supply  and  return  marns, 
radiators,  and  expansion  tank  at  the  highest  point  of  the  entire 
system.  All  the  pipes,  radiators,  tanks,  heaters,  etc.,  are  filled  with 
water.  This  entire  volume  has  to  be  heated  before  its  effects  are  felt 
in  the  rooms,  and  must  cool  off  again  before  the  rooms  will  cool. 
It  gives  a  very  equable  and  satisfactory  temperature,  but  is  more  suit- 
able for  rigorous  climates  than  comparatively  mild  ones.  Great  care 
is  required  in  laying  out  a  hot-water  plant  to  insure  efficient  circu- 
lation. 

In  a  general  way,  indirect  hot  water  is  the  most  expensive  system, 
indirect  steam  next,  then  direct  hot  water,  and  finally  direct  steam. 

Open  fires  and  hot-air  furnaces  are  still  often  used  in  private  houses. 
Both  are  satisfactory  under  certain  conditions,  but  neither  can  be 
recommended  for  general  application. 

PLUMBING 

The  object  of  the  plumbing  in  a  house  or  building  is  to  supply 
water  and  gas  at  the  necessary  points,  and  to  carry  off  all  liquid  and 
solid  waste,  into  the  sewers  or  other  systems  of  disposal.  Piping  a 
house  for  gas  and  water  is  comparatively  simple.  The  other  matters 
are  more  complicated.  The  various  fixtures  connected  with  the 
drains  comprise  water  closets,  baths,  lavatories,  kitchen  and  pantry 
sinks,  urinals,  laundry  tubs,  and  slop  sinks.  These  must  all  be  con- 
nected by  suitable  pipes  with  the  drains  and  sewers.  The  drains  in 


37 

the  house  are  known,  in  a  general  way,  as  soil  pipes.  All  sewers  are 
filled  with  offensive  gases;  it  has  been  very  generally  believed  that 
these  gases  were  a  source  of  disease;  while  this  danger  is  probably 
exaggerated,  sewer  gas  is  a  most  unpleasant  constituent  of  the  air  in 
a  dwelling  house.  Even  the  soil  pipe  in  a  house  becomes  foul  enough 
to  be  a  source  of  disagreeable  odors;  drains  leading  from  wash  basins, 
baths,  sinks,  and  tubs,  become  coated  with  a  slimy,  ill-smelling;  de- 
posit on  the  inside.  An  ideal  system  of  plumbing  provides  for  cut- 
ting off  the  house  from  all  these  sources  of  bad  odors,  just  as  near  the 
various  fixtures  as  possible.  The  means  used  is  always  a  trap  in  the 
drain  itself,  so  arranged  as  to  provide  a  water  seal  between  the  house 
and  the  drains.  All  parts  of  the  waste  pipe  between  the  traps  and 
the  house  should  be  accessible  for  inspection  and  cleaning.  It  is  also 
found  necessary  to  provide  for  a  free  circulation  of  air  through  the 
soil  pipes  to  secure  the  best  results,  and  to  prevent  a  discharge  of 
water  from  a  fixture  above,  from  syphoning  off  the  water  in  a  trap  be- 
low, thus  leaving  the  house  open  to  the  drains.  As  the  house  is 
usually  warmer  than  the  ground,  especially  in  the  winter,  there  is 
nearly  always  an  inward  draft,  tending  to  draw  air  from  sewers  into 
the  house. 

Two  prints*  are  attached  hereto,  showing  two  ways  of  piping  a 
house.  In  one,  a  connection  is  made  -from  the  sewer  side  of  every 
trap  to  the  open  air,  above  all  fixtures,  with  the  idea  of  securing  cir- 
culation and  a  supply  of  air  to  restore  the  pressure  when  a  discharge 
passes  through  the  adjacent  soil  pipe,  thus  preventing  the  water  seal 
in  the  trap  from  breaking.  In  the  other,  these  "back-air  vents,"  as 
they  are  called,  are  omitted,  but  the  ends  of  all  wastes  are  carried  to 
the  open  air  above  all  fixtures.  This  is  just  as  good  and  somewhat 
simpler  than  the  other  plan,  although  it  takes  more  pipe.  This  lat- 
ter system  provides  for  an  exceedingly  thorough  circulation  in  all  the 
drain  pipes.  There  are  some  persons  who  object  to  the  fresh-air 
inlet  in  front  of  the  house,  as  it  sometimes  emits  foul  odors  from  the 
house  drains.  But,  on  the  whole,  it  seems  better  to  retain  it,  as  the 
amount  of  fouling  in  the  house  pipes  is  not  very  great,  and  the  draft 
will  generally  be  in  at  the  fresh-air  jnlet  and  out  through  the  pipe  at 
the  top  of  the  house.  If  any  opening  is  made  on  the  sewer  side  of 
the  house  trap,  it  must  always  be  carried  above  the  roof.  All  traps 
should  have  means  of  getting  at  them  to  clean  them  out  without 
breaking  the  drains.  This  is  indicated  by  the  letters  C.  O.  on  the 
drawings.  All  clean-out  openings  must  be  stopped  gas  tight  and 
water  tight  with  a  plug,  and  opened  up  only  when  the  trap  needs  at- 

*Not  printed. 


38 

tention.  For  soil  pipe,  cast-iron  and  steel  are  used.  Cast-iron 
soil  pipe  comes  in  lengths  of  5  feet,  with  hubs  and  spigots  for  calk- 
ing. There  are  two  weights,  standard  and  extra  heavy;  the  latter 
should  always  be  used.  The  pipes  should  be  dipped,  hot,  into  melted 
asphalt  or  coal  tar,  so  as  to  give  them  a  thorough  coating,  both  in- 
side and  out.  Fittings  for  cast-iron  soil  pipe  should  all  be  of  the 
long  turn  or. sanitary  kind,  to  reduce  friction  and  prevent  deposits. 
Steel  pipe,  for  waste  purposes,  should  be  extra  heavy,  and  used  with 
the  special  recessed  drainage  fittings  to  be  found  in  the  catalogues  of 
the  best  makers.  These  recessed  fittings  have  shoulders  inside  against 
which  the  pipe  abuts.  The  shoulder  is  of  the  same  thickness  as  the 
pipe  and  insures  a  continuous  smooth  surface  on  the  inside.  Where 
steel  pipe  and  screwed  fittings  are  used,  flanged  joints  should  be  in- 
troduced at  convenient  points,  so  that  if  repairs  or  changes  necessitate 
breaking  the  line  of  pipe,  it  can  be  done  with  a  minimum  of  damage 
and  expense.  Steel  drainage  pipes  are  sometimes  galvanized;  this  is 
good  for  the  outside  of  the  pipe,  but  of  doubtful  value  on  the  inside; 
decomposing  animal  matter  gives  rise  to  acids,  and  if  the  inside  of  the 
pipe  is  galvanized  there  will  be  galvanic  action,  which  will  be  quite 
deleterious,  and  hasten  the  destruction  of  the  pipe.  There  is  no 
reason  why  steel  drainage  pipes  should  not  be  dipped  in  hot  asphalt; 
the  result  would  be  better. 

After  the  question  of  pipes  is  settled,  there  remains  the  fixtures  and 
traps.  The  ideal  plumbing  fixture  is  made  of  vitreous  ware,  practi- 
cally like  porcelain.  It  has  a  hard  surface  glaze,  but  is  vitreous  all 
the  way  through,  so  that  if  the  glaze  is  cracked,  it  will  not  absorb 
any  unclean  fluids.  It  is  free  of  crazing — i.  e.,  cracking  of  the  glaze, 
and  is  made  as  nearly  as  possible  in  one  piece,  without  joints  or  other 
places  where  dirt  can  collect.  There  are  only  two  concerns  in  the 
United  States  making  thoroughly  first-class  plumbing  material.  One 
of  these  is  the  J.  L.  Mott  Iron  Works,  and  the  other  is  the  Meyers- 
Sniffen  Co.,  both  of  New  York.  There  are  a  number  of  large  job- 
bing houses  that  handle  plumbing  materials  and  fixtures,  but  they 
handle  many  grades  besides  the  best.  The  Mott  Works  make  some 
cheaper  goods  for  which  there 'is  a  deman'd,  but  they  can  be  trusted 
not  to  sell  them  for  anything  except  what  they  are.  The  jobbers 
may  be  perfectly  reliable  in  matters  of  this  kind,  but  some  of  them 
are  not.  It  is  understood  the  Meyers-Sniffen  Co.  does  not  handle 
any  of  the  cheaper  grades  of  plumbing  materials  at  all. 

Some  fixtures,  such  as  bath  tubs,  very  heavy  water  closets,  slop 
sinks,  pantry  sinks,  etc.,  have  to  be  made  so  thick  that  they  can  not 


39 

be  made  of  the  vitreous  ware,  which  can  be  burned  only  in  thin 
pieces.  The  heavier  sections  are  made  with  a  fire  clay  body  and  a 
hard  glaze.  The  maker  should  guarantee  them  against  crazing,  and 
the  fire  clay  body  should  be  almost  vitrified. 

The  only  way  to  test  the  quality  of  porcelain  fixtures  is  to  break 
them  across  and  test  them  for  strength  and  absorption.  Vitreous 
ware,  or,  as  the  Mott  catalogues  call  it,  vitro-adamant,  should  be  ab- 
solutely non-absorbent  all  the  way  through.  The  fire  clay  wares  will 
absorb  a  certain  amount  of  water;  but  they  should  be  burned  so 
hard  that  if  hydrostatic  pressure  be  introduced  into  the  pores,  the 
ware  will  not  crumble  to  pieces  under  less  than  1,500  pounds  per 
square  inch,  or  more.  It  is  possible  to  form  a  very  fair  idea  of  the 
degree  to  which  fire  clay  has  been  burned  by  simply  testing  its  hard- 
ness. The  same  is  true,  to  a  limited  extent,  of  the  vitreous  ware. 

Any  plumbing  fixture,  in  addition  to  being  made  of  thoroughly 
sanitary,  non-absorbent  material,  must  be  of  a  proper  shape  and  size. 
This  can  best  be  illustrated  by  considering  the  case  of  the  water 
closet.  This  fixture,  in  its  early  form,  consisted  of  a  porcelain  or 
porcelain  lined  bowl,  with  a  movable  pan  for  a  bottom.  When  the 
closet  was  used,  a  handle  was  pulled,  which  dumped  the  pan,  flushed 
the  bowl,  and  filled  the  pan  again  with  water.  The  pan  was  dumped 
into  a  sort  of  hopper  which  communicated  with  the  soil  pipe  through 
a  trap.  The  sides  of  the  hopper  formed  a  large  inaccessible  surface, 
which  soon  became  very  foul.  An  improvement  in  this  consisted  in 
the  use  of  a  bowl  emptying  into  a  trap  through  an  opening  closed  by 
a  plunger  valve.  The  bowl  had  a  flushing  rim  and  could  be  kept  fairly 
clean,  but  there  was  much  fouling  space  around  the  plunger.  Then 
came  a  porcelain  bowl  or  hopper,  with  a  flushing  rim,  supplied  from 
a  tank.  This  was  the  first  really  successful  solution;  but  the  surface 
of  water  presented  for  the  reception  of  excrement  was  small,  and  the 
sides  of  the  bowl  became  soiled  and  required  much  attention.  An 
attempt  to  remedy  this  led  to  the  form  known  as  the  washout  closet, 
which  was  really  a  step  backwards.  Then  the  hopper  and  trap  were 
combined  in  one  piece  of  porcelain,  and  efforts  made  to  enlarge  the 
water  surface.  It  was  found  impracticable  to  make  this  ferm  flush 
properly  with  a  large  water  surface;  moreover,  it  would  not  flush 
successfully  with  a  very  deep  seal  in  the  trap.  Not  over  an  inch  seal 
was  used  at  first.  By  dint  of  much  experimenting,  forms  of  the 
simple  combined  hopper  and  trap  have  been  developed  which  present 
a  reasonably  large  water  surface,  have  a  seal  of  nearly  2  inches,  and 
flush  very  successfully.  For  use  in  public  places  these  are  to-day  the 


40 

most  desirable  forms.  But  a  modification,  known  as  the  syphon  jet 
closet,  is  better  for  private  houses.  In  this  form  a  part  of  the  flush 
is  directed  through  a  jet  arm,  which  discharges  at  the  bottom  of  the 
trap  upwards  and  towards  the  soil  pipe.  This  enables  a  very  large 
body  of  water  to  be  maintained  in  the  bowl,  with  a  very  deep  seal — 
as  much  as  3  inches,  in  some  cases.  The  jet  moves  the  entire 
volume  of  water  along,  together.  As  soon  as  it  begins  to  pass  through 
the  outlet  a  vacuum  is  created,  and  the  contents  of  the  bowl  are 
ejected  by  syphonic  action  with  a  rush.  The  bowl  then  refills  from 
the  flush.  The  outlets  of  all  syphonic  closets  have  a  rather  tortuous 
form;  this  is  to  retard  the  water  enough  to  form  a  partial  vacuum 
in  the  outlet  itself.  It  has  been  found  possible  in  the  case  of  a  wash- 
down  closet — which  is  another  name  for  the  combined  hopper  and 
trap — to  secure  some  syphonic  action  by  enlarging  the  outlet  and  then 
contracting  it  again,  and  also  by  making  it  more  or  less  tortuous.  This 
has  made  a  deeper  seal  possible,  which  is  a  matter  of  great  importance. 
The  limits  of  time  and  space  prevent  further  discussion  of  plumb- 
ing fixtures  and  many  other  points  that  require  attention  in  buildings, 
but  it  is  hoped  that  the  fragmentary  notes  contained  herein  may  prove 
of  some  value  and  smooth  out  a  few  of  the  difficulties  that  present 
themselves  to  a  young  engineer  engaged  for  the  first  time  in  the 
erection  of  a  building. 


